Build: move name 'python.so' to Make variable

Allow the user to change the name of the generated shared object by
specifying an alternate $GCC_PYTHON_PLUGIN_SO on the command line.

Author: Kevin Pyle

Makefile

@@ -97,6 +97,8 @@ PYTHON_CONFIG=python-config
 PYTHON_INCLUDES=$(shell $(PYTHON_CONFIG) --includes)
 PYTHON_LIBS=$(shell $(PYTHON_CONFIG) --libs)
 
+GCC_PYTHON_PLUGIN_SO	:= python.so
+
 CPPFLAGS+= -I$(GCCPLUGINS_DIR)/include -I$(GCCPLUGINS_DIR)/include/c-family -I. $(PYTHON_INCLUDES)
 # Allow user to pick optimization, choose whether warnings are fatal,
 # and choose debugging information level.
@@ -110,9 +112,9 @@ endif
 
 all: autogenerated-config.h testcpybuilder test-suite testcpychecker
 
-plugin: autogenerated-config.h python.so
+plugin: autogenerated-config.h $(GCC_PYTHON_PLUGIN_SO)
 
-python.so: $(PLUGIN_OBJECT_FILES)
+$(GCC_PYTHON_PLUGIN_SO): $(PLUGIN_OBJECT_FILES)
 	$(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS) -shared $^ -o $@ $(LIBS)
 
 $(PLUGIN_OBJECT_GENERATED_FILES): CPPFLAGS+= $(if $(srcdir),-I$(srcdir))
@@ -145,7 +147,7 @@ autogenerated-variable.c: autogenerated-gimple-types.txt $(srcdir)maketreetypes.
 # Doing so seems to require that paths be absolute, rather than relative
 # to this directory
 TEST_CFLAGS= \
-  -fplugin=$(CURDIR)/python.so \
+  -fplugin=$(CURDIR)/$(GCC_PYTHON_PLUGIN_SO) \
   -fplugin-arg-python-script=test.py
 
 # A catch-all test for quick experimentation with the API: