Remove cflags and ldflags from crt defaults

After ToolchainCflags were added to soong crt no longer needs to try to
recreate the bare minimum cflags for compiling for each architecture.
Also always use GCC to match crt.mk

Change-Id: I01a833ab70d989033c84f072e3660d060189688c

libc/Android.bp

@@ -1946,30 +1946,24 @@ cc_defaults {
     arch: {
         arm: {
             local_include_dirs: ["arch-arm/include"],
-            cflags: ["-mthumb-interwork"],
         },
         arm64: {
             local_include_dirs: ["arch-arm64/include"],
         },
         mips: {
             local_include_dirs: ["arch-mips/include"],
-            ldflags: ["-melf32ltsmip"],
         },
         mips64: {
             local_include_dirs: ["arch-mips64/include"],
-            ldflags: ["-melf64ltsmip"],
         },
         x86: {
-            cflags: ["-m32"],
-            ldflags: ["-melf_i386"],
             local_include_dirs: ["arch-x86/include"],
         },
         x86_64: {
-            cflags: ["-m64"],
-            ldflags: ["-melf_x86_64"],
             local_include_dirs: ["arch-x86_64/include"],
         },
     },
+    clang: false,
 }
 
 cc_defaults {