gcc-with-cpychecker: Add CC_FOR_CPYCHECKER

gcc-with-cpychecker does not use CC to find gcc, in order to avoid forkbombing
when setting CC=gcc-with-cpychecker, and instead uses a hardcoded 'gcc'.  This
means that when we want to use a specific gcc, we either needs to edit
gcc-with-cpychecker to adjust the filename, or use PATH settings to pick up
gcc (which may mean having to map somehow f.i. 'gcc-7' to 'gcc').

Add handling of CC_FOR_CPYCHECKER in gcc-with-cpychecker, to be able to easily
specify the gcc to be used.

Author: vries

Makefile

@@ -132,7 +132,7 @@ plugin: autogenerated-config.h $(PLUGIN_DSO)
 # When running the plugin from a working copy, use LD_LIBARY_PATH=gcc-c-api
 # so that the plugin can find its libgcc-c-api.so there
 #
-INVOCATION_ENV_VARS := LD_LIBRARY_PATH=gcc-c-api CC=$(CC)
+INVOCATION_ENV_VARS := CC_FOR_CPYCHECKER=$(CC) LD_LIBRARY_PATH=gcc-c-api CC=$(CC)
 
 # When installing, both the plugin and libgcc-c-api.so will be installed to
 # $(GCCPLUGINS_DIR), so we give the plugin an RPATH of $(GCCPLUGINS_DIR)

gcc-with-cpychecker

@@ -74,9 +74,14 @@ dictstr += ', "maxtrans":%i' % ns.maxtrans
 dictstr += ', "dump_json":%i' % ns.dump_json
 cmd = 'from libcpychecker import main; main(**{%s})' % dictstr
 
-# (Do not look up CC in the environment, to avoid forkbombing
-# when setting CC=gcc-with-cpychecker)
-args = ['gcc',
+# Do not use CC in the environment, to avoid forkbombing when setting
+# CC=gcc-with-cpychecker.  Instead, use CC_FOR_CPYCHECKER.
+if 'CC_FOR_CPYCHECKER' in os.environ:
+    gcc = os.environ['CC_FOR_CPYCHECKER']
+else:
+    gcc = 'gcc'
+
+args = [gcc,
         ('-fplugin=%s' % PLUGIN),
         ('-fplugin-arg-python-command=%s' % cmd)]
 args += other_args # (the args we didn't consume)