Makefile: Use ctxt.BuildTags for static build tags

Right now, we add build flags to most every Go command in order to
enable a certain set of features. This is quite tedious, and naturally
there are some invocations of Go commands which do not currently have
those tags set. As a result, some may be built inconsistently, but more
importantly manually running e.g. `go test ./...` will not use any of
those build tags at all.

There's an obscure way to configure build tags such that they're always
on, which is the "ctxt.BuildTags" file. It is mostly undocumented,
except for one small excerpt in `go doc build`:

    During a particular build, the following words are satisfied:

    - the target operating system, as spelled by runtime.GOOS
    ...
    - "go1.14", from Go version 1.14 onward
    - any additional words listed in ctxt.BuildTags

So it does at least seem to be officially supported, even though it's
not that well known.

Let's use it to avoid any inconsistencies. Furthermore, it will help us
when reintroducing Git2Go into our build dependencies, which will make
specifying some build tags mandatory.

2 files changed, 8 insertions, 6 deletions

diff --git a/Makefile b/Makefile
index a823a01c0..cf9c95a43 100644
--- a/Makefile
+++ b/Makefile
@@ -50,7 +50,6 @@ BUILD_TIME      := $(shell date +"%Y%m%d.%H%M%S")
 GITALY_VERSION  := $(shell git describe --match v* 2>/dev/null | sed 's/^v//' || cat ${SOURCE_DIR}/VERSION 2>/dev/null || echo unknown)
 GO_LDFLAGS      := -ldflags '-X ${GITALY_PACKAGE}/internal/version.version=${GITALY_VERSION} -X ${GITALY_PACKAGE}/internal/version.buildtime=${BUILD_TIME}'
 GO_TEST_LDFLAGS := -X gitlab.com/gitlab-org/gitaly/auth.timestampThreshold=5s
-GO_BUILD_TAGS   := tracer_static tracer_static_jaeger continuous_profiler_stackdriver
 
 # Dependency versions
 GOLANGCI_LINT_VERSION ?= 1.27.0
@@ -123,7 +122,7 @@ all: install
 
 .PHONY: build
 build: ${SOURCE_DIR}/.ruby-bundle
-	go install ${GO_LDFLAGS} -tags "${GO_BUILD_TAGS}" $(addprefix ${GITALY_PACKAGE}/cmd/, $(call find_commands))
+	go install ${GO_LDFLAGS} $(addprefix ${GITALY_PACKAGE}/cmd/, $(call find_commands))
 
 .PHONY: install
 install: build
@@ -172,17 +171,17 @@ test: test-go rspec rspec-gitlab-shell
 test-go: prepare-tests ${GO_JUNIT_REPORT}
 	${Q}mkdir -p ${TEST_REPORT_DIR}
 	${Q}echo 0>${TEST_EXIT}
-	${Q}go test ${TEST_OPTIONS} -v -tags "${GO_BUILD_TAGS}" -ldflags='${GO_TEST_LDFLAGS}' -count=1 $(call find_go_packages) 2>&1 | tee ${TEST_OUTPUT} || echo $$? >${TEST_EXIT}
+	${Q}go test ${TEST_OPTIONS} -v -ldflags='${GO_TEST_LDFLAGS}' -count=1 $(call find_go_packages) 2>&1 | tee ${TEST_OUTPUT} || echo $$? >${TEST_EXIT}
 	${Q}${GO_JUNIT_REPORT} <${TEST_OUTPUT} >${TEST_REPORT}
 	${Q}exit `cat ${TEST_EXIT}`
 
 .PHONY: test-with-proxies
 test-with-proxies: prepare-tests
-	${Q}go test -tags "${GO_BUILD_TAGS}" -count=1  -exec ${SOURCE_DIR}/_support/bad-proxies ${GITALY_PACKAGE}/internal/rubyserver/
+	${Q}go test -count=1  -exec ${SOURCE_DIR}/_support/bad-proxies ${GITALY_PACKAGE}/internal/rubyserver/
 
 .PHONY: test-with-praefect
 test-with-praefect: build prepare-tests
-	${Q}GITALY_TEST_PRAEFECT_BIN=${BUILD_DIR}/bin/praefect go test -tags "${GO_BUILD_TAGS}" -ldflags='${GO_TEST_LDFLAGS}' -count=1 $(call find_go_packages) # count=1 bypasses go 1.10 test caching
+	${Q}GITALY_TEST_PRAEFECT_BIN=${BUILD_DIR}/bin/praefect go test -ldflags='${GO_TEST_LDFLAGS}' -count=1 $(call find_go_packages) # count=1 bypasses go 1.10 test caching
 
 .PHONY: race-go
 race-go: TEST_OPTIONS = -race
@@ -270,7 +269,7 @@ docker:
 	cp -r  ${GITALY_RUBY_DIR} ${BUILD_DIR}/docker/ruby
 	${Q}rm -rf ${BUILD_DIR}/docker/ruby/vendor/bundle
 	for command in $(call find_commands); do \
-		GOOS=linux GOARCH=amd64 go build -tags "${GO_BUILD_TAGS}" ${GO_LDFLAGS} -o "${BUILD_DIR}/docker/bin/$${command}" ${GITALY_PACKAGE}/cmd/$${command}; \
+		GOOS=linux GOARCH=amd64 go build ${GO_LDFLAGS} -o "${BUILD_DIR}/docker/bin/$${command}" ${GITALY_PACKAGE}/cmd/$${command}; \
 	done
 	cp ${SOURCE_DIR}/Dockerfile ${BUILD_DIR}/docker/
 	docker build -t gitlab/gitaly:v${GITALY_VERSION} -t gitlab/gitaly:latest ${BUILD_DIR}/docker/
diff --git a/ctxt.BuildTags b/ctxt.BuildTags
new file mode 100644
index 000000000..defa606e9
--- /dev/null
+++ b/ctxt.BuildTags
@@ -0,0 +1,3 @@
+continuous_profiler_stackdriver
+tracer_static
+tracer_static_jaeger