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
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -4474,7 +4474,7 @@ 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
--- a/gcc/incpath.c
+++ b/gcc/incpath.c
@@ -472,8 +472,8 @@ 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);
 
@@ -484,7 +484,7 @@ 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", INC_BRACKET);
+  add_env_var_paths ("CROSS_CPATH", INC_BRACKET);
   add_env_var_paths (lang_env_vars[idx], INC_SYSTEM);
 
   target_c_incpath.extra_pre_includes (sysroot, iprefix, stdinc);
diff --git a/gcc/system.h b/gcc/system.h
--- a/gcc/system.h
+++ b/gcc/system.h
@@ -1244,4 +1244,6 @@ void gcc_stablesort (void *, size_t, size_t,
    of the number.  */
 #define PRsa(n) "%" #n PRIu64 "%c"
 
+#define LIBRARY_PATH_ENV "CROSS_LIBRARY_PATH"
+
 #endif /* ! GCC_SYSTEM_H */