MIPS: Remove -U__unix and -U__unix__ from cflags

Leave '__unix' and '__unix__' defined on mips/mips64, like arm.
This is needed to avoid a warning in external/libcxx project.

Test: successful build and boot aosp_mips-eng
Test: successful build and boot aosp_mips64-eng

Change-Id: I8f0e17bdbeffd5078c19aa7506564b8e79a9c945
diff --git a/cc/config/mips64_device.go b/cc/config/mips64_device.go
index 35fa551..e05dbf1 100644
--- a/cc/config/mips64_device.go
+++ b/cc/config/mips64_device.go
@@ -28,8 +28,6 @@
 		"-fomit-frame-pointer",
 		"-fno-strict-aliasing",
 		"-funswitch-loops",
-		"-U__unix",
-		"-U__unix__",
 		"-Umips",
 		"-ffunction-sections",
 		"-fdata-sections",
diff --git a/cc/config/mips_device.go b/cc/config/mips_device.go
index d154426..78e95b6 100644
--- a/cc/config/mips_device.go
+++ b/cc/config/mips_device.go
@@ -28,8 +28,6 @@
 		"-fomit-frame-pointer",
 		"-fno-strict-aliasing",
 		"-funswitch-loops",
-		"-U__unix",
-		"-U__unix__",
 		"-Umips",
 		"-ffunction-sections",
 		"-fdata-sections",