[make] only compile infer by default

Summary: Define `default` target at the very top of the Makefile to make sure some other target doesn't replace it, as was done accidentally in D5498555

Reviewed By: martinoluca

Differential Revision: D5536691

fbshipit-source-id: 7398ec0

Makefile

@@ -5,6 +5,9 @@
 # LICENSE file in the root directory of this source tree. An additional grant
 # of patent rights can be found in the PATENTS file in the same directory.
 
+.PHONY: default
+default: infer
+
 ROOT_DIR = .
 include $(ROOT_DIR)/Makefile.config
 
@@ -92,9 +95,6 @@ build_waf_test: build_make_test
 build_waf_print: build_make_print
 endif
 
-.PHONY: all
-all: infer
-
 ifeq ($(IS_INFER_RELEASE),no)
 configure: configure.ac $(wildcard m4/*.m4)
 #	rerun ./autogen.sh in case of failure as the failure may be due to needing to rerun