set pipefail option when running tests (pulumi#1600)

When running the tests in CI, we're piping the output of `go test` into
gotestfmt to get prettier output. This works because `gotestfmt` will
return a non-zero exit code when there are test failures.

However when there are other failures, e.g. compilation of the tests
failed, `gotestfmt` will have a 0 exit code. `go test` wouldn't, but
because we're piping the results through, the shell swallows that unless
we're setting the pipefail option.

Set up the pipefail option here, so tests aren't accidentally green when
compilation fails.

/cc @thomas11 who noticed the tests were passing even though compilation
failed in pulumi#1595

Makefile

@@ -13,15 +13,15 @@ lint:
  tslint -c tslint.json **/*.ts
 
 only_test:
- cd misc/test && go test -json ./... --timeout 4h -v -count=1 -short -parallel 40 --tags=all | gotestfmt
+ bash -c 'set -o pipefail && cd misc/test && go test -json ./... --timeout 4h -v -count=1 -short -parallel 40 --tags=all | gotestfmt'
 
 specific_test_set:
  echo "running $(TestSet) Acceptance Tests"
- cd misc/test && go test -json . --timeout 4h -v -count=1 -short -parallel 40 --tags=all --run=TestAcc$(TestSet) | gotestfmt
+ bash -c 'set -o pipefail && cd misc/test && go test -json . --timeout 4h -v -count=1 -short -parallel 40 --tags=all --run=TestAcc$(TestSet) | gotestfmt'
 
 specific_tag_set:
  echo "running $(TagSet)$(TestSet) Acceptance Tests"
- cd misc/test && go test -json . --timeout 4h -v -count=1 -short -parallel 40 --tags=$(TagSet) --run=TestAcc$(TagSet)$(TestSet) | gotestfmt
+ bash -c 'set -o pipefail && cd misc/test && go test -json . --timeout 4h -v -count=1 -short -parallel 40 --tags=$(TagSet) --run=TestAcc$(TagSet)$(TestSet) | gotestfmt'
 
 performance_test_set:
  cd misc/test && go test . --timeout 4h -count=1 -short -parallel 40 --tags=Performance