unix: merge duplicate code in zerrors_linux_*.go

Run mkmerge.go on zerrors_linux_*.go to merge duplicate consts, funcs,
and types into zerrors_linux.go

Please see https://gist.github.com/jupj/639b5cda305d251161fec2304c27c9b9
for a script to validate these changes.

Updates golang/go#33059

Change-Id: I168b5efc7fd6d2fcf7fc8dfe1ef5eea07f07f9c2
Reviewed-on: https://go-review.googlesource.com/c/sys/+/221318
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/linux/mkall.go

@@ -187,6 +187,13 @@ func main() {
 		}
 	}
 
+	fmt.Printf("----- GENERATING: merging generated files -----\n")
+	if err := mergeFiles(); err != nil {
+		fmt.Printf("%v\n***** FAILURE:    merging generated files *****\n\n", err)
+	} else {
+		fmt.Printf("----- SUCCESS:    merging generated files -----\n\n")
+	}
+
 	fmt.Printf("----- GENERATING ptrace pairs -----\n")
 	ok := true
 	for _, p := range ptracePairs {
@@ -549,6 +556,25 @@ func (t *target) mksyscallFlags() (flags []string) {
 	return
 }
 
+// Merge all the generated files for Linux targets
+func mergeFiles() error {
+	// Setup environment variables
+	os.Setenv("GOOS", runtime.GOOS)
+	os.Setenv("GOARCH", runtime.GOARCH)
+
+	// Merge each of the four type of files
+	for _, ztyp := range []string{"zerrors"} {
+		cmd := makeCommand("go", "run", "mkmerge.go", "-out", fmt.Sprintf("%s_%s.go", ztyp, GOOS), fmt.Sprintf("%s_%s_*.go", ztyp, GOOS))
+		err := cmd.Run()
+		if err != nil {
+			return fmt.Errorf("could not merge %s files: %w", ztyp, err)
+		}
+		fmt.Printf("%s files merged\n", ztyp)
+	}
+
+	return nil
+}
+
 // generatePtracePair takes a pair of GOARCH values that can run each
 // other's binaries, such as 386 and amd64. It extracts the PtraceRegs
 // type for each one. It writes a new file defining the types