golang: Ignore GOFLAGS, GO111MODULE environment variables

These were added in Go 1.11.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

lang/golang/golang-values.mk

@@ -13,7 +13,7 @@ include $(GO_INCLUDE_DIR)/golang-version.mk
 
 
 unexport \
-  GOARCH GOBIN GOCACHE GODEBUG GOHOSTARCH GOOS GOPATH GORACE GOROOT GOTMPDIR GCCGO \
+  GOARCH GOBIN GOCACHE GODEBUG GOFLAGS GOHOSTARCH GOOS GOPATH GORACE GOROOT GOTMPDIR GCCGO \
   CGO_ENABLED \
   CGO_CFLAGS CGO_CFLAGS_ALLOW CGO_CFLAGS_DISALLOW \
   CGO_CPPFLAGS CGO_CPPFLAGS_ALLOW CGO_CPPFLAGS_DISALLOW \
@@ -21,6 +21,7 @@ unexport \
   CGO_FFLAGS CGO_FFLAGS_ALLOW CGO_FFLAGS_DISALLOW \
   CGO_LDFLAGS CGO_LDFLAGS_ALLOW CGO_LDFLAGS_DISALLOW \
   GOARM GO386 GOMIPS GOMIPS64 \
+  GO111MODULE \
   GOROOT_FINAL GO_EXTLINK_ENABLED GIT_ALLOW_PROTOCOL \
   CC_FOR_TARGET CXX_FOR_TARGET GO_DISTFLAGS GO_GCFLAGS GO_LDFLAGS GOBUILDTIMELOGFILE GOROOT_BOOTSTRAP \
   BOOT_GO_GCFLAGS GOEXPERIMENT GOBOOTSTRAP_TOOLEXEC