github: Fix "no space left on device" issue in CI

.github/workflows/test.yml

@@ -24,9 +24,7 @@ jobs:
         name: Free Disk Space (Ubuntu)
         uses: jlumbroso/free-disk-space@54081f138730dfa15788a46383842cd2f914a1be # v1.3.1
         with:
-          # this might remove tools that are actually needed,
-          # if set to "true" but frees about 6 GB
-          tool-cache: false
+          tool-cache: true
           android: true
           dotnet: true
           haskell: true

magefile.go

@@ -70,6 +70,10 @@ func flagEnv() map[string]string {
 	}
 }
 
+func emptyEnv() map[string]string {
+	return map[string]string{}
+}
+
 // Generate autogen packages
 func Generate() error {
 	generatorPackages := []string{
@@ -138,6 +142,9 @@ func Docker() error {
 func Check() {
 	if runtime.GOARCH == "amd64" && runtime.GOOS != "darwin" {
 		mg.Deps(Test386)
+		if isCI() {
+			mg.Deps(CleanTest)
+		}
 	} else {
 		fmt.Printf("Skip Test386 on %s and/or %s\n", runtime.GOARCH, runtime.GOOS)
 	}
@@ -151,6 +158,9 @@ func Check() {
 	// don't run two tests in parallel, they saturate the CPUs anyway, and running two
 	// causes memory issues in CI.
 	mg.Deps(TestRace)
+	if isCI() {
+		mg.Deps(CleanTest)
+	}
 }
 
 func testGoFlags() string {
@@ -161,6 +171,11 @@ func testGoFlags() string {
 	return "-timeout=1m"
 }
 
+// Clean Go's test cache.
+func CleanTest() error {
+	return runCmd(emptyEnv(), goexe, "clean", "-testcache")
+}
+
 // Run tests in 32-bit mode
 // Note that we don't run with the extended tag. Currently not supported in 32 bit.
 func Test386() error {