Makefile: try to fix Go version detection in `sanity-checks`

- set the Go version to 1.12.x for Travis

.travis.yml

@@ -1,4 +1,4 @@
-language: c
+language: go
 
 # https://docs.travis-ci.com/user/caching/
 cache:
@@ -13,6 +13,9 @@ git:
   # disable LFS file downloading during regular cloning
   lfs_skip_smudge: true
 
+go:
+  - "1.12.x"
+
 matrix:
   include:
     - os: linux

Makefile

@@ -23,7 +23,7 @@ $(SILENT_TARGET_PREFIX).SILENT:
 sanity-checks:
 	@ [[ "$$PWD" =~ /vendor/nim-beacon-chain$ && -e ../../Makefile && -e ../../common.mk ]] || \
 		{ echo -e "This Makefile can only be used from the corresponding Git submodule in the Nimbus repository.\nDetailed instructions available in README.md or online at https://github.com/status-im/nim-beacon-chain/#building-and-testing"; exit 1; }
-	@+ $(MAKE) --silent -C ../../ sanity-checks
+	@+ bash -c "$(MAKE) --silent -C ../../ sanity-checks"
 
 deps: | sanity-checks
 	@+ $(MAKE) --silent -C ../../ deps