cmd/dist: enforce the lowest bootstrap version

The go1.24 release notes say that go1.22.6 is the
minimum bootstraps required,
the go team also use go1.22.6 bootstraps in testing,
so if there's a problem with using an older version,
automated testing won't uncover it.

Now enforce this in dist to avoid
release notes that do not match reality, which can be confusing.

For #64751

Change-Id: I8d50770e19f7f014e1316f0ac872e288a27c20fe

Author: qiulaidongfeng

src/cmd/dist/buildtool.go

@@ -123,6 +123,8 @@ var tryDirs = []string{
 	"go1.22.6",
 }
 
+var minBootStrapVersion [3]string = [3]string{"1", "22", "6"}
+
 func bootstrapBuildTools() {
 	goroot_bootstrap := os.Getenv("GOROOT_BOOTSTRAP")
 	if goroot_bootstrap == "" {
@@ -134,6 +136,19 @@ func bootstrapBuildTools() {
 			}
 		}
 	}
+
+	// check bootstrap version.
+	ver := run(pathf("%s/bin", goroot_bootstrap), CheckExit, pathf("%s/bin/go", goroot_bootstrap), "version")
+	_, after, _ := strings.Cut(ver, "go1")
+	if after != "" {
+		v := strings.Split(after, ".")
+		if len(v) > 2 {
+			if v[0] < minBootStrapVersion[1] || v[1] < minBootStrapVersion[2] {
+				fatalf("requires Go 1.%s.%s or later for bootstrap", minBootStrapVersion[1], minBootStrapVersion[2])
+			}
+		}
+	}
+
 	xprintf("Building Go toolchain1 using %s.\n", goroot_bootstrap)
 
 	mkbuildcfg(pathf("%s/src/internal/buildcfg/zbootstrap.go", goroot))