cmd/go: fix test failures with -count=2

In each test, either set the -n flag to avoid writing build artifacts
to the cache, or set GOCACHE explicitly to point to a clean cache.

Tested manually with 'go test -count=2 cmd/go'.

Fixes #37820

Change-Id: I24403e738b1a10d5fe9dc8d98ef27a76ebe2704a
Reviewed-on: https://go-review.googlesource.com/c/go/+/223140
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -7,7 +7,8 @@ env GO111MODULE=off
 [!linux] skip  # test only works if c-archive implies -shared
 [short] skip
 
-go build -x -buildmode=c-archive -gcflags=all=-shared=false ./override.go
+env GOCACHE=$WORK/gocache  # Looking for compile commands, so need a clean cache.
+go build -x -n -buildmode=c-archive -gcflags=all=-shared=false ./override.go
 stderr '^.*/compile (.* )?-shared (.* )?-shared=false'
 
 -- override.go --

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

@@ -1,15 +1,16 @@
 [short] skip
 [!cgo] skip
 
-go run -x main.go
+env GOCACHE=$WORK/gocache  # Looking for compile flags, so need a clean cache.
+go build -x -n main.go
 stderr '"-I[^"]+c flags"' # find quoted c flags
-! stderr '"-I[^"]+c flags".*"-I[^"]+c flags"' # don't find too many quoted c flags
+! stderr '"-I[^"]+c flags".*"-I[^"]+c flags"' # don't find too many quoted c flags per line
 stderr '"-L[^"]+ld flags"' # find quoted ld flags
-! stderr '"-L[^"]+c flags".*"-L[^"]+c flags"' # don't find too many quoted ld flags
+! stderr '"-L[^"]+c flags".*"-L[^"]+c flags"' # don't find too many quoted ld flags per line
 
 -- main.go --
 package main
 // #cgo CFLAGS: -I"c flags"
 // #cgo LDFLAGS: -L"ld flags"
 import "C"
-func main() {}
+func main() {}

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

@@ -3,6 +3,8 @@ env GO111MODULE=off
 [!gc] skip 'using -gcflags and -ldflags'
 [short] skip
 
+env GOCACHE=$WORK/gocache  # Looking for compile commands, so need a clean cache.
+
 # -gcflags=-e applies to named packages, not dependencies
 go build -n -v -gcflags=-e z1 z2
 stderr 'compile.* -e.* -p z1'

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

@@ -14,6 +14,9 @@ go get -d golang.org/x/text@14c0d48
 
 # dropping -d, we should see a build.
 [short] skip
+
+env GOCACHE=$WORK/gocache  # Looking for compile commands, so need a clean cache.
+
 go get -x golang.org/x/text/language@14c0d48
 stderr 'compile|cp|gccgo .*language\.a$'
 

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

@@ -14,7 +14,8 @@ stdout 'rsc.io/quote v1.5.2'
 [short] skip
 
 # Packages that are only imported in excluded files should not be built.
-go get -x .
+env GOCACHE=$WORK/gocache  # Looking for compile commands, so need a clean cache.
+go get -n -x .
 stderr 'compile.* -p m '
 ! stderr 'compile.* -p example.com/version '
 ! stderr 'compile.* -p rsc.io/quote '