main: do not set working directory for Clang invocation

This commit avoids setting the working directory to the TinyGo root when
invocating Clang. This helps to weed out issues before we add support
for bundling Clang in a release.

builtins.go

@@ -243,7 +243,6 @@ func compileBuiltins(target string, callback func(path string) error) error {
 		cmd := exec.Command(commands["clang"], "-c", "-Oz", "-g", "-Werror", "-Wall", "-std=c11", "-fshort-enums", "-nostdlibinc", "-ffunction-sections", "-fdata-sections", "--target="+target, "-fdebug-prefix-map="+dir+"="+remapDir, "-o", objpath, srcpath)
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
-		cmd.Dir = dir
 		err = cmd.Run()
 		if err != nil {
 			return &commandError{"failed to build", srcpath, err}

main.go

@@ -62,9 +62,19 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 		config.gc = spec.GC
 	}
 
-	// Append command line passed CFlags and LDFlags
-	spec.CFlags = append(spec.CFlags, config.cFlags...)
-	spec.LDFlags = append(spec.LDFlags, config.ldFlags...)
+	root := sourceDir()
+
+	// Merge and adjust CFlags.
+	cflags := append([]string{}, config.cFlags...)
+	for _, flag := range spec.CFlags {
+		cflags = append(cflags, strings.Replace(flag, "{root}", root, -1))
+	}
+
+	// Merge and adjust LDFlags.
+	ldflags := append([]string{}, config.ldFlags...)
+	for _, flag := range spec.LDFlags {
+		ldflags = append(ldflags, strings.Replace(flag, "{root}", root, -1))
+	}
 
 	compilerConfig := compiler.Config{
 		Triple:        spec.Triple,
@@ -73,11 +83,11 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 		GOARCH:        spec.GOARCH,
 		GC:            config.gc,
 		PanicStrategy: config.panicStrategy,
-		CFlags:        spec.CFlags,
-		LDFlags:       spec.LDFlags,
+		CFlags:        cflags,
+		LDFlags:       ldflags,
 		Debug:         config.debug,
 		DumpSSA:       config.dumpSSA,
-		RootDir:       sourceDir(),
+		RootDir:       root,
 		GOPATH:        getGopath(),
 		BuildTags:     spec.BuildTags,
 	}
@@ -203,22 +213,22 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 		// Prepare link command.
 		executable := filepath.Join(dir, "main")
 		tmppath := executable // final file
-		ldflags := append(spec.LDFlags, "-o", executable, objfile, "-L", sourceDir())
+		ldflags := append(ldflags, "-o", executable, objfile, "-L", root)
 		if spec.RTLib == "compiler-rt" {
 			ldflags = append(ldflags, librt)
 		}
 
 		// Compile extra files.
 		for i, path := range spec.ExtraFiles {
+			abspath := filepath.Join(root, path)
 			outpath := filepath.Join(dir, "extra-"+strconv.Itoa(i)+"-"+filepath.Base(path)+".o")
 			cmdName := spec.Compiler
 			if name, ok := commands[cmdName]; ok {
 				cmdName = name
 			}
-			cmd := exec.Command(cmdName, append(spec.CFlags, "-c", "-o", outpath, path)...)
+			cmd := exec.Command(cmdName, append(cflags, "-c", "-o", outpath, abspath)...)
 			cmd.Stdout = os.Stdout
 			cmd.Stderr = os.Stderr
-			cmd.Dir = sourceDir()
 			err := cmd.Run()
 			if err != nil {
 				return &commandError{"failed to build", path, err}
@@ -235,10 +245,9 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 				if name, ok := commands[cmdName]; ok {
 					cmdName = name
 				}
-				cmd := exec.Command(cmdName, append(spec.CFlags, "-c", "-o", outpath, path)...)
+				cmd := exec.Command(cmdName, append(cflags, "-c", "-o", outpath, path)...)
 				cmd.Stdout = os.Stdout
 				cmd.Stderr = os.Stderr
-				cmd.Dir = sourceDir()
 				err := cmd.Run()
 				if err != nil {
 					return &commandError{"failed to build", path, err}

targets/nrf51.json

@@ -6,7 +6,7 @@
 		"--target=armv6m-none-eabi",
 		"-Qunused-arguments",
 		"-DNRF51",
-		"-Ilib/CMSIS/CMSIS/Include"
+		"-I{root}/lib/CMSIS/CMSIS/Include"
 	],
 	"ldflags": [
 		"-T", "targets/nrf51.ld"

targets/nrf52.json

@@ -7,7 +7,7 @@
 		"-mfloat-abi=soft",
 		"-Qunused-arguments",
 		"-DNRF52832_XXAA",
-		"-Ilib/CMSIS/CMSIS/Include"
+		"-I{root}/lib/CMSIS/CMSIS/Include"
 	],
 	"ldflags": [
 		"-T", "targets/nrf52.ld"

targets/nrf52840.json

@@ -7,7 +7,7 @@
 		"-mfloat-abi=soft",
 		"-Qunused-arguments",
 		"-DNRF52840_XXAA",
-		"-Ilib/CMSIS/CMSIS/Include"
+		"-I{root}/lib/CMSIS/CMSIS/Include"
 	],
 	"ldflags": [
 		"-T", "targets/nrf52840.ld"