cmd/go: don't leave test binary around for coverage

It's not needed to analyze coverage data.
Fixes #6120

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/13343050

src/cmd/go/doc.go

@@ -269,7 +269,7 @@ List packages
 
 Usage:
 
-	go list [-e] [-f format] [-json] [-tags 'tag list'] [packages]
+	go list [-e] [-race] [-f format] [-json] [-tags 'tag list'] [packages]
 
 List lists the packages named by the import paths, one per line.
 
@@ -345,6 +345,9 @@ a non-nil Error field; other information may or may not be missing
 The -tags flag specifies a list of build tags, like in the 'go build'
 command.
 
+The -race flag causes the package data to include the dependencies
+required by the race detector.
+
 For more about specifying packages, see 'go help packages'.
 
 
@@ -809,8 +812,8 @@ will compile the test binary and then run it as
 
 	pkg.test -test.v -test.cpuprofile=prof.out -dir=testdata -update
 
-The test flags that generate profiles also leave the test binary in pkg.test
-for use when analyzing the profiles.
+The test flags that generate profiles (other than for coverage) also
+leave the test binary in pkg.test for use when analyzing the profiles.
 
 Flags not recognized by 'go test' must be placed after any specified packages.
 

src/cmd/go/test.go

@@ -213,8 +213,8 @@ will compile the test binary and then run it as
 
 	pkg.test -test.v -test.cpuprofile=prof.out -dir=testdata -update
 
-The test flags that generate profiles also leave the test binary in pkg.test
-for use when analyzing the profiles.
+The test flags that generate profiles (other than for coverage) also
+leave the test binary in pkg.test for use when analyzing the profiles.
 
 Flags not recognized by 'go test' must be placed after any specified packages.
 `,
@@ -272,6 +272,7 @@ var (
 	testCoverPaths   []string   // -coverpkg flag
 	testCoverPkgs    []*Package // -coverpkg flag
 	testProfile      bool       // some profiling flag
+	testNeedBinary   bool       // profile needs to keep binary around
 	testI            bool       // -i flag
 	testV            bool       // -v flag
 	testFiles        []string   // -file flag(s)  TODO: not respected
@@ -728,7 +729,7 @@ func (b *builder) test(p *Package) (buildAction, runAction, printAction *action,
 	a.target = filepath.Join(testDir, testBinary) + exeSuffix
 	pmainAction := a
 
-	if testC || testProfile {
+	if testC || testNeedBinary {
 		// -c or profiling flag: create action to copy binary to ./test.out.
 		runAction = &action{
 			f:      (*builder).install,

src/cmd/go/testflag.go

@@ -181,6 +181,7 @@ func testFlags(args []string) (packageNames, passToTest []string) {
 			testTimeout = value
 		case "blockprofile", "cpuprofile", "memprofile":
 			testProfile = true
+			testNeedBinary = true
 		case "coverpkg":
 			testCover = true
 			if value == "" {