Refactor bionic includes into a single place

Bionic includes are the same on all architectures, modulo
architecture-specific includes.  Use a single function to populate the
list, passing in bionic's and the kernel's names for the architecture.

Also get rid of the ${LibcRoot} variable, it is not providing any value
and makes grepping harder.

Change-Id: I39e7907d312f52dd1378a3937ab1bcba12c4e97f
diff --git a/cc/mips64_device.go b/cc/mips64_device.go
index 19f9caf..a1ec3a2 100644
--- a/cc/mips64_device.go
+++ b/cc/mips64_device.go
@@ -100,14 +100,7 @@
 	pctx.StaticVariable("mips64Cflags", strings.Join(mips64Cflags, " "))
 	pctx.StaticVariable("mips64Ldflags", strings.Join(mips64Ldflags, " "))
 	pctx.StaticVariable("mips64Cppflags", strings.Join(mips64Cppflags, " "))
-	pctx.StaticVariable("mips64IncludeFlags", strings.Join([]string{
-		"-isystem ${LibcRoot}/arch-mips64/include",
-		"-isystem ${LibcRoot}/include",
-		"-isystem ${LibcRoot}/kernel/uapi",
-		"-isystem ${LibcRoot}/kernel/android/uapi",
-		"-isystem ${LibcRoot}/kernel/common",
-		"-isystem ${LibcRoot}/kernel/uapi/asm-mips",
-	}, " "))
+	pctx.StaticVariable("mips64IncludeFlags", bionicHeaders("mips64", "mips"))
 
 	// Clang cflags
 	pctx.StaticVariable("mips64ClangTriple", "mips64el-linux-android")