cmd/go: in script tests, avoid checking non-main packages for staleness

Non-main packages in module mode should not be installed to
GOPATH/pkg, but due to #37015 they were installed there anyway.
Lacking a proper install location, 'go install' becomes a no-op
for non-main packages in module mode.

This change switches the 'go install' commands in the test_fuzz_cache
and build_overlay tests to instead use 'go build', using the '-x' flag
to check for compile commands instead of querying 'go list' about
staleness.

For #37015.

Change-Id: I56d80cf2a43efb6163c62082c86cd3e4f0ff73c1
Reviewed-on: https://go-review.googlesource.com/c/go/+/417095
Run-TryBot: Bryan Mills <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
Reviewed-by: Russ Cox <[email protected]>

src/cmd/go/testdata/script/build_overlay.txt

@@ -47,20 +47,24 @@ go build -overlay overlay.json -o main_call_asm$GOEXE ./call_asm
 exec ./main_call_asm$GOEXE
 ! stdout .
 
-# Change the contents of a file in the overlay and ensure that makes the target stale
-go install -overlay overlay.json ./test_cache
-go list -overlay overlay.json -f '{{.Stale}}' ./test_cache
-stdout '^false$'
-cp overlay/test_cache_different.go overlay/test_cache.go
-go list -overlay overlay.json -f '{{.Stale}}' ./test_cache
-stdout '^true$'
-
 [cgo] go list -compiled -overlay overlay.json -f '{{range .CompiledGoFiles}}{{. | printf "%s\n"}}{{end}}' ./cgo_hello_replace
 [cgo] cp stdout compiled_cgo_sources.txt
 [cgo] go run ../print_line_comments.go compiled_cgo_sources.txt
 [cgo] stdout $GOPATH[/\\]src[/\\]m[/\\]cgo_hello_replace[/\\]cgo_hello_replace.go
 [cgo] ! stdout $GOPATH[/\\]src[/\\]m[/\\]overlay[/\\]hello.c
 
+# Change the contents of a file in the overlay and ensure that makes the target stale
+env OLD_GOCACHE=$GOCACHE
+env GOCACHE=$WORK/cache  # use a fresh cache so that multiple runs of the test don't interfere
+go build -x -overlay overlay.json ./test_cache
+stderr '(compile|gccgo)( |\.exe).*test_cache.go'
+go build -x -overlay overlay.json ./test_cache
+! stderr '(compile|gccgo)( |\.exe).*test_cache.go'  # cached
+cp overlay/test_cache_different.go overlay/test_cache.go
+go build -x -overlay overlay.json ./test_cache
+stderr '(compile|gccgo)( |\.exe).*test_cache.go'  # not cached
+env CACHE=$OLD_GOCACHE
+
 # Run same tests but with gccgo.
 env GO111MODULE=off
 [!exec:gccgo] stop

src/cmd/go/testdata/script/test_fuzz_cache.txt

@@ -17,15 +17,12 @@ go clean -cache
 exists $GOCACHE/fuzz
 
 # 'go clean -fuzzcache' should delete the fuzz cache but not the build cache.
-go list -f {{.Stale}} ./empty
-stdout true
-go install ./empty
-go list -f {{.Stale}} ./empty
-stdout false
+go build -x ./empty
+stderr '(compile|gccgo)( |\.exe).*empty.go'
 go clean -fuzzcache
 ! exists $GOCACHE/fuzz
-go list -f {{.Stale}} ./empty
-stdout false
+go build -x ./empty
+! stderr '(compile|gccgo)( |\.exe).*empty.go'
 
 # Fuzzing indicates that one new interesting value was found with an empty
 # corpus, and the total size of the cache is now 1.