Add Clang Asflags for mips

Like make, it needs -fPIC to be added to compile successfully.

Change-Id: I1d6f1388c42a84f331bbce1ecd669669441d986e

cc/cc.go

@@ -566,6 +566,7 @@ func (c *CCBase) collectFlags(ctx common.AndroidModuleContext, toolchain Toolcha
 		flags.GlobalFlags = append(flags.GlobalFlags, instructionSetFlags)
 
 		if flags.Clang {
+			flags.AsFlags = append(flags.AsFlags, toolchain.ClangAsflags())
 			flags.CppFlags = append(flags.CppFlags, "${commonClangGlobalCppflags}")
 			flags.GlobalFlags = append(flags.GlobalFlags,
 				toolchain.ClangCflags(),

cc/mips_device.go

@@ -211,6 +211,10 @@ func (t *toolchainMips) ToolchainClangCflags() string {
 	return t.toolchainClangCflags
 }
 
+func (t *toolchainMips) ClangAsflags() string {
+	return "-fPIC"
+}
+
 func (t *toolchainMips) ClangCflags() string {
 	return t.clangCflags
 }

cc/toolchain.go

@@ -60,6 +60,7 @@ type Toolchain interface {
 	ClangSupported() bool
 	ClangTriple() string
 	ToolchainClangCflags() string
+	ClangAsflags() string
 	ClangCflags() string
 	ClangCppflags() string
 	ClangLdflags() string
@@ -112,6 +113,10 @@ func (toolchainBase) ExecutableSuffix() string {
 	return ""
 }
 
+func (toolchainBase) ClangAsflags() string {
+	return ""
+}
+
 type toolchain64Bit struct {
 	toolchainBase
 }