gnu: Add gcc-arm-none-eabi-7-2018-q2-update.

* gnu/packages/embedded.scm (gcc-arm-none-eabi-7-2018-q2-update): New
variable.
* gnu/packages/patches/gcc-7-cross-environment-variables.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/local.mk

@@ -871,6 +871,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gcc-6-source-date-epoch-1.patch		\
   %D%/packages/patches/gcc-6-source-date-epoch-2.patch		\
   %D%/packages/patches/gcc-7-cross-mingw.patch			\
+  %D%/packages/patches/gcc-7-cross-environment-variables.patch	\
   %D%/packages/patches/gcc-8-cross-environment-variables.patch	\
   %D%/packages/patches/gcc-8-strmov-store-file-names.patch	\
   %D%/packages/patches/gcc-9-asan-fix-limits-include.patch	\

gnu/packages/embedded.scm

@@ -207,6 +207,84 @@ (define-public newlib-nano-arm-none-eabi
            "--disable-nls"))))
     (synopsis "Newlib variant for small systems with limited memory")))
 
+
+;;; The following definitions are for the "7-2018-q2-update" variant of the
+;;; ARM cross toolchain as offered on https://developer.arm.com
+(define-public gcc-arm-none-eabi-7-2018-q2-update
+  (let ((xgcc (cross-gcc "arm-none-eabi"
+                         #:xgcc gcc-7
+                         #:xbinutils (cross-binutils "arm-none-eabi")))
+        (revision "1")
+        (svn-revision 261907))
+    (package (inherit xgcc)
+      (version (string-append "7-2018-q2-update-"
+                              revision "." (number->string svn-revision)))
+      (source
+       (origin
+         (method svn-fetch)
+         (uri (svn-reference
+               (url "svn://gcc.gnu.org/svn/gcc/branches/ARM/embedded-7-branch/")
+               (revision svn-revision)))
+         (file-name (string-append "gcc-arm-embedded-" version "-checkout"))
+         (sha256
+          (base32
+           "192ggs63bixf3irpijgfkjks73yx1r3a4i6grk1y0i0iny76pmx5"))
+         (patches
+          (append
+           (origin-patches (package-source gcc-7))
+           (search-patches "gcc-7-cross-environment-variables.patch")))))
+      (native-inputs
+       `(("gcc" ,gcc-5)
+         ("flex" ,flex)
+         ("isl" ,isl-0.18)
+         ,@(alist-delete "isl" (package-native-inputs xgcc))))
+      (arguments
+       (substitute-keyword-arguments (package-arguments xgcc)
+         ((#:phases phases)
+          `(modify-phases ,phases
+             (add-after 'unpack 'expand-version-string
+               (lambda _
+                 (make-file-writable "gcc/DEV-PHASE")
+                 (with-output-to-file "gcc/DEV-PHASE"
+                   (lambda ()
+                     (display "7-2018-q2-update")))
+                 #t))
+             (add-after 'unpack 'fix-genmultilib
+               (lambda _
+                 (substitute* "gcc/genmultilib"
+                   (("#!/bin/sh") (string-append "#!" (which "sh"))))
+                 #t))))
+         ((#:configure-flags flags)
+          ;; The configure flags are largely identical to the flags used by the
+          ;; "GCC ARM embedded" project.
+          `(append (list "--enable-multilib"
+                         "--with-newlib"
+                         "--with-multilib-list=rmprofile"
+                         "--with-host-libstdcxx=-static-libgcc -Wl,-Bstatic,-lstdc++,-Bdynamic -lm"
+                         "--enable-plugins"
+                         "--disable-decimal-float"
+                         "--disable-libffi"
+                         "--disable-libgomp"
+                         "--disable-libmudflap"
+                         "--disable-libquadmath"
+                         "--disable-libssp"
+                         "--disable-libstdcxx-pch"
+                         "--disable-nls"
+                         "--disable-shared"
+                         "--disable-threads"
+                         "--disable-tls")
+                   (delete "--disable-multilib" ,flags)))))
+      (native-search-paths
+       (list (search-path-specification
+              (variable "CROSS_C_INCLUDE_PATH")
+              (files '("arm-none-eabi/include")))
+             (search-path-specification
+              (variable "CROSS_CPLUS_INCLUDE_PATH")
+              (files '("arm-none-eabi/include")))
+             (search-path-specification
+              (variable "CROSS_LIBRARY_PATH")
+              (files '("arm-none-eabi/lib"))))))))
+
 (define (make-libstdc++-arm-none-eabi xgcc newlib)
   (let ((libstdc++ (make-libstdc++ xgcc)))
     (package (inherit libstdc++)

gnu/packages/patches/gcc-7-cross-environment-variables.patch

@@ -0,0 +1,67 @@
+Search path environment variables for cross-compilers.  See the discussion
+at <http://gcc.gnu.org/ml/gcc/2013-02/msg00124.html>.
+
+Note: Touch 'C_INCLUDE_PATH' et al. rather than 'CPATH', as discussed
+at <http://bugs.gnu.org/22186>.
+
+diff --git a/gcc/gcc.c b/gcc/gcc.c
+index eced0d5..08dec2b 100644
+--- a/gcc/gcc.c
++++ b/gcc/gcc.c
+@@ -4317,7 +4317,7 @@ process_command (unsigned int decoded_options_count,
+     }
+ 
+   temp = env.get (LIBRARY_PATH_ENV);
+-  if (temp && *cross_compile == '0')
++  if (temp)
+     {
+       const char *startp, *endp;
+       char *nstore = (char *) alloca (strlen (temp) + 3);
+diff --git a/gcc/incpath.c b/gcc/incpath.c
+index 98fe5ec..96aff65 100644
+--- a/gcc/incpath.c
++++ b/gcc/incpath.c
+@@ -461,8 +461,8 @@ register_include_chains (cpp_reader *pfile, const char *sysroot,
+ 			 int stdinc, int cxx_stdinc, int verbose)
+ {
+   static const char *const lang_env_vars[] =
+-    { "C_INCLUDE_PATH", "CPLUS_INCLUDE_PATH",
+-      "OBJC_INCLUDE_PATH", "OBJCPLUS_INCLUDE_PATH" };
++    { "CROSS_C_INCLUDE_PATH", "CROSS_CPLUS_INCLUDE_PATH",
++      "CROSS_OBJC_INCLUDE_PATH", "CROSS_OBJCPLUS_INCLUDE_PATH" };
+   cpp_options *cpp_opts = cpp_get_options (pfile);
+   size_t idx = (cpp_opts->objc ? 2: 0);
+ 
+@@ -473,7 +473,7 @@ register_include_chains (cpp_reader *pfile, const char *sysroot,
+ 
+   /* CPATH and language-dependent environment variables may add to the
+      include chain.  */
+-  add_env_var_paths ("CPATH", BRACKET);
++  add_env_var_paths ("CROSS_CPATH", BRACKET);
+   add_env_var_paths (lang_env_vars[idx], SYSTEM);
+ 
+   target_c_incpath.extra_pre_includes (sysroot, iprefix, stdinc);
+diff --git a/gcc/system.h b/gcc/system.h
+index 0cbf60a..3242c68 100644
+--- a/gcc/system.h
++++ b/gcc/system.h
+@@ -1169,4 +1169,6 @@ helper_const_non_const_cast (const char *p)
+ /* Get definitions of HOST_WIDE_INT.  */
+ #include "hwint.h"
+ 
++#define LIBRARY_PATH_ENV "CROSS_LIBRARY_PATH"
++
+ #endif /* ! GCC_SYSTEM_H */
+diff --git a/gcc/tlink.c b/gcc/tlink.c
+index a2a7db0..2d96872 100644
+--- a/gcc/tlink.c
++++ b/gcc/tlink.c
+@@ -456,7 +456,7 @@ recompile_files (void)
+   file *f;
+ 
+   putenv (xstrdup ("COMPILER_PATH="));
+-  putenv (xstrdup ("LIBRARY_PATH="));
++  putenv (xstrdup (LIBRARY_PATH_ENV "="));
+ 
+   while ((f = file_pop ()) != NULL)
+     {