[travis] fix travis and install

Summary:
`brew install opam` is unhappy and wants us to run `brew unlink python`
beforehand so do that.

The `make install` logic in infer had a problem of nested `if` logic.

Reviewed By: da319

Differential Revision: D7686760

fbshipit-source-id: dd0c988

.travis.yml

@@ -9,6 +9,7 @@ before_install:
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get -qq update; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get install -y aspcud; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew unlink python; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install opam; fi
 install:
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then travis_wait 60 ./build-infer.sh --yes java --opam-switch 4.06.1 --only-setup-opam; fi

Makefile

@@ -544,7 +544,6 @@ ifdef DESTDIR
 ifeq (,$(findstring :/,:$(DESTDIR)))
 #	DESTDIR is set and relative
 	$(MAKE) -C facebook install 'DESTDIR=../$(DESTDIR)'
-endif
 else
 #	DESTDIR is set and absolute
 	$(MAKE) -C facebook install
@@ -553,6 +552,7 @@ else
 #	DESTDIR not set
 	$(MAKE) -C facebook install
 endif
+endif
 
 # Nuke objects built from OCaml. Useful when changing the OCaml compiler, for instance.
 .PHONY: ocaml_clean