Revert "cmd/go: don't copy cgo files to objdir when overlay is present"

This reverts CL 265758.

Reason for revert: longtest builders were failing

Change-Id: Ic6c3f3759399e45c1625c7c57f7aa67a1d90c601
Reviewed-on: https://go-review.googlesource.com/c/go/+/268900
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Trust: Jay Conrod <jayconrod@google.com>

src/cmd/go/internal/work/exec.go

@@ -2732,20 +2732,6 @@ OverlayLoop:
 		}
 	}
 
-	// Rewrite overlaid paths in cgo files.
-	// cgo adds //line and #line pragmas in generated files with these paths.
-	var trimpath []string
-	for i := range cgofiles {
-		path := mkAbs(p.Dir, cgofiles[i])
-		if opath, ok := fsys.OverlayPath(path); ok {
-			cgofiles[i] = opath
-			trimpath = append(trimpath, opath+"=>"+path)
-		}
-	}
-	if len(trimpath) > 0 {
-		cgoflags = append(cgoflags, "-trimpath", strings.Join(trimpath, ";"))
-	}
-
 	if err := b.run(a, execdir, p.ImportPath, cgoenv, cfg.BuildToolexec, cgoExe, "-objdir", objdir, "-importpath", p.ImportPath, cgoflags, "--", cgoCPPFLAGS, cgoCFLAGS, cgofiles); err != nil {
 		return nil, nil, err
 	}

src/cmd/go/testdata/script/build_overlay.txt

@@ -43,12 +43,6 @@ go build -overlay overlay.json -o main_cgo_angle$GOEXE ./cgo_hello_angle
 exec ./main_cgo_angle$GOEXE
 stdout '^hello cgo\r?\n'
 
-go list -compiled -overlay -f '{{range .CompiledGoFiles}}{{. | printf "%s\n"}}{{end}}' ./cgo_hello_replace
-cp stdout compiled_cgo_sources.txt
-go run ../print_line_comments.go compiled_cgo_sources.txt
-stdout $GOPATH/src/m/cgo_hello_replace/cgo_hello_replace.go
-!stdout $GOPATH/src/m/overlay/hello.c
-
 # Run same tests but with gccgo.
 env GO111MODULE=off
 [!exec:gccgo] stop
@@ -213,33 +207,3 @@ void say_hello() { puts("hello cgo\n"); fflush(stdout); }
 
 void say_hello() { puts("hello cgo\n"); fflush(stdout); }
 
--- print_line_comments.go --
-package main
-
-import (
-    "fmt"
-    "io/ioutil"
-    "log"
-    "os"
-    "strings"
-)
-
-func main() {
-    compiledGoFilesArg := os.Args[1]
-    b, err := ioutil.ReadFile(compiledGoFilesArg)
-    if err != nil {
-        log.Fatal(err)
-    }
-    compiledGoFiles := strings.Split(strings.TrimSpace(string(b)), "\n")
-    for _, f := range compiledGoFiles {
-        b, err := ioutil.ReadFile(f)
-        if err != nil {
-            log.Fatal(err)
-        }
-        for _, line := range strings.Split(string(b), "\n") {
-            if strings.HasPrefix(line, "#line") || strings.HasPrefix(line, "//line") {
-                fmt.Println(line)
-            }
-        }
-    }
-}