remove a couple of pieces of dead code (#272)

We no longer cache the obfuscated source code for -debugdir, so
obfSrcArchive is entirely useless at this point. We likely didn't notice
because the Go compiler doesn't realise it's unused.

symAbis is also unnecessary. It used to be necessary as we could only
collect the action ID from transformCompile in the second asm
invocation. Since we no longer need the temporary file dance with
transformCompile, we can simplify that code too.

main.go

@@ -4,9 +4,7 @@
 package main
 
 import (
-	"archive/tar"
 	"bytes"
-	"compress/gzip"
 	"encoding/base64"
 	"encoding/binary"
 	"errors"
@@ -415,23 +413,9 @@ var transformFuncs = map[string]func([]string) (args []string, _ error){
 func transformAsm(args []string) ([]string, error) {
 	flags, paths := splitFlagsFromFiles(args, ".s")
 
-	symAbis := false
-	// Note that flagValue only supports "-foo=true" bool flags, but the std
-	// flag is generally just "-std".
-	// TODO: Better support boolean flags for the tools.
-	for _, flag := range flags {
-		if flag == "-gensymabis" {
-			symAbis = true
-		}
-	}
-
-	// If we are generating symbol ABIs, the output does not actually
-	// contain the package import path. Exported APIs show up as "".FooBar.
-	// Otherwise, we are assembling, and the import path does make its way
-	// into the output object file.
-	// To obfuscate the path in the -p flag, we need the current action ID,
-	// which we recover from the file that transformCompile wrote for us.
-	if !symAbis && curPkg.Name != "main" && curPkg.Private {
+	// When assembling, the import path can make its way into the output
+	// object file.
+	if curPkg.Name != "main" && curPkg.Private {
 		flags = flagSetValue(flags, "-p", curPkg.obfuscatedImportPath())
 	}
 
@@ -545,13 +529,6 @@ func transformCompile(args []string) ([]string, error) {
 		detachedComments[i], files[i] = comments, file
 	}
 
-	obfSrcArchive := &bytes.Buffer{}
-	obfSrcGzipWriter := gzip.NewWriter(obfSrcArchive)
-	defer obfSrcGzipWriter.Close()
-
-	obfSrcTarWriter := tar.NewWriter(obfSrcGzipWriter)
-	defer obfSrcTarWriter.Close()
-
 	// If this is a package to obfuscate, swap the -p flag with the new
 	// package path.
 	newPkgPath := ""
@@ -672,18 +649,6 @@ func transformCompile(args []string) ([]string, error) {
 			return nil, err
 		}
 
-		if err := obfSrcTarWriter.WriteHeader(&tar.Header{
-			Name:    name,
-			Mode:    0o755,
-			ModTime: time.Now(), // Need for restoring obfuscation time
-			Size:    int64(obfSrc.Len()),
-		}); err != nil {
-			return nil, err
-		}
-		if _, err := obfSrcTarWriter.Write(obfSrc.Bytes()); err != nil {
-			return nil, err
-		}
-
 		newPaths = append(newPaths, tempFile.Name())
 	}
 	flags = flagSetValue(flags, "-importcfg", newImportCfg)