Merge pull request #99 from moomalade/make_cc_override

Enable Makefile environment overrides for CC,CXX and AR.

src/actions/make/make_cpp.lua

@@ -359,17 +359,23 @@
 	function make.cppTools(cfg, toolset)
 		local tool = toolset.gettoolname(cfg, "cc")
 		if tool then
-			_p('  CC = %s', tool)
+			_p('  ifeq ($(origin CC), default)')
+			_p('    CC = %s', tool)
+			_p('  endif' )
 		end
 
 		tool = toolset.gettoolname(cfg, "cxx")
 		if tool then
-			_p('  CXX = %s', tool)
+			_p('  ifeq ($(origin CXX), default)')
+			_p('    CXX = %s', tool)
+			_p('  endif' )
 		end
 
 		tool = toolset.gettoolname(cfg, "ar")
 		if tool then
-			_p('  AR = %s', tool)
+			_p('  ifeq ($(origin AR), default)')
+			_p('    AR = %s', tool)
+			_p('  endif' )
 		end
 
 		tool = toolset.gettoolname(cfg, "rc")

tests/actions/make/cpp/test_clang.lua

@@ -31,9 +31,15 @@
 		make.cppConfigs(prj)
 		test.capture [[
 ifeq ($(config),debug)
-  CC = clang
-  CXX = clang++
-  AR = ar
+  ifeq ($(origin CC), default)
+    CC = clang
+  endif
+  ifeq ($(origin CXX), default)
+    CXX = clang++
+  endif
+  ifeq ($(origin AR), default)
+    AR = ar
+  endif
   		]]
 	end