sys/targets: better detection for missing/broken cross-compilers

1. Detect when compiler is present, but is not functioning
(can't build a simple program, common for Linux distros).

2. Be more strict with skipping tests due to missing/broken compilers on CI
(on CI they should work, so fail loudly if not).

3. Dedup this logic across syz-env and pkg/csource tests.

4. Add better error reporting for syz-env.

Fixes #1606

1 files changed, 19 insertions, 15 deletions

diff --git a/tools/syz-env/env.go b/tools/syz-env/env.go
index aa0143ab9..81a40af8a 100644
--- a/tools/syz-env/env.go
+++ b/tools/syz-env/env.go
@@ -6,7 +6,6 @@ package main
 import (
 	"fmt"
 	"os"
-	"os/exec"
 	"runtime"
 	"strconv"
 	"strings"
@@ -16,6 +15,22 @@ import (
 )
 
 func main() {
+	vars, err := impl()
+	if err != nil {
+		fmt.Printf("export SYZERROR=%v\n", err)
+		os.Exit(1)
+	}
+	for _, v := range vars {
+		fmt.Printf("export %v=%v\\n", v.Name, v.Val)
+	}
+}
+
+type Var struct {
+	Name string
+	Val  string
+}
+
+func impl() ([]Var, error) {
 	hostOS := or(os.Getenv("HOSTOS"), runtime.GOOS)
 	hostArch := or(os.Getenv("HOSTARCH"), runtime.GOARCH)
 	targetOS := or(os.Getenv("TARGETOS"), hostOS)
@@ -23,12 +38,7 @@ func main() {
 	targetVMArch := or(os.Getenv("TARGETVMARCH"), targetArch)
 	target := targets.Get(targetOS, targetArch)
 	if target == nil {
-		fmt.Printf("unknown target %v/%v\n", targetOS, targetArch)
-		os.Exit(1)
-	}
-	type Var struct {
-		Name string
-		Val  string
+		return nil, fmt.Errorf("unknown target %v/%v", targetOS, targetArch)
 	}
 	parallelism := runtime.NumCPU()
 	if mem := osutil.SystemMemorySize(); mem != 0 {
@@ -53,15 +63,9 @@ func main() {
 		{"NCORES", strconv.Itoa(parallelism)},
 		{"EXE", target.ExeExtension},
 		{"NATIVEBUILDOS", target.BuildOS},
+		{"NO_CROSS_COMPILER", target.BrokenCrossCompiler},
 	}
-	if targetOS != runtime.GOOS {
-		if _, err := exec.LookPath(target.CCompiler); err != nil {
-			vars = append(vars, Var{"NO_CROSS_COMPILER", "yes"})
-		}
-	}
-	for _, v := range vars {
-		fmt.Printf("export %v=%v\\n", v.Name, v.Val)
-	}
+	return vars, nil
 }
 
 func or(s1, s2 string) string {