Add -fdebug-compilation-dir option

The main use of this flag is to be to make both the debug info
and the build command line be independent of the compilation dir.
See: https://reviews.llvm.org/D63387 & https://blog.llvm.org/2019/11/deterministic-builds-with-clang-and-lld.html

Removed -fdebug-prefix-map and PWD variable being set in the compile
command line - these were workarounds we originally did to ensure that
the compile output is independent of the working directory and are no
longer needed now that we have -fdebug-compilation-dir.

Test: Ran "m
out/target/product/crosshatch/obj/SHARED_LIBRARIES/libexif.vendor_intermediates/same_vndk_variants.timestamp"
which fails on an RBE hardened stack without this change and passes with
this change.

Bug: b/169266636
Change-Id: Ib0f271e55f6cf0c89a30e65d3a0b25fe3f3a8f48

cc/builder.go

@@ -44,14 +44,14 @@ var (
 		blueprint.RuleParams{
 			Depfile:     "${out}.d",
 			Deps:        blueprint.DepsGCC,
-			Command:     "$relPwd ${config.CcWrapper}$ccCmd -c $cFlags -MD -MF ${out}.d -o $out $in",
+			Command:     "${config.CcWrapper}$ccCmd -c $cFlags -MD -MF ${out}.d -o $out $in",
 			CommandDeps: []string{"$ccCmd"},
 		},
 		"ccCmd", "cFlags")
 
 	ccNoDeps = pctx.AndroidStaticRule("ccNoDeps",
 		blueprint.RuleParams{
-			Command:     "$relPwd $ccCmd -c $cFlags -o $out $in",
+			Command:     "$ccCmd -c $cFlags -o $out $in",
 			CommandDeps: []string{"$ccCmd"},
 		},
 		"ccCmd", "cFlags")
@@ -220,7 +220,7 @@ var (
 			Labels:       map[string]string{"type": "abi-dump", "tool": "header-abi-dumper"},
 			ExecStrategy: "${config.REAbiDumperExecStrategy}",
 			Platform: map[string]string{
-				remoteexec.PoolKey:      "${config.RECXXPool}",
+				remoteexec.PoolKey: "${config.RECXXPool}",
 			},
 		}, []string{"cFlags", "exportDirs"}, nil)
 

cc/config/global.go

@@ -53,6 +53,13 @@ var (
 		"-Werror=pragma-pack",
 		"-Werror=pragma-pack-suspicious-include",
 		"-Werror=unreachable-code-loop-increment",
+
+		// -fdebug-compilation-dir=. is used to make both the action command line and the output
+		// independent of the working directory of the action.
+		// Using cc1 flags since RBE's input processor does not yet have the updated version
+		// of LLVM that promotes the cc1 flag to driver level flag.
+		// See: https://reviews.llvm.org/D63387
+		"-Xclang,-fdebug-compilation-dir,.",
 	}
 
 	commonGlobalConlyflags = []string{}
@@ -150,10 +157,6 @@ var (
 var pctx = android.NewPackageContext("android/soong/cc/config")
 
 func init() {
-	if android.BuildOs == android.Linux {
-		commonGlobalCflags = append(commonGlobalCflags, "-fdebug-prefix-map=/proc/self/cwd=")
-	}
-
 	pctx.StaticVariable("CommonGlobalConlyflags", strings.Join(commonGlobalConlyflags, " "))
 	pctx.StaticVariable("DeviceGlobalCppflags", strings.Join(deviceGlobalCppflags, " "))
 	pctx.StaticVariable("DeviceGlobalLdflags", strings.Join(deviceGlobalLdflags, " "))