[PATCH 4/4] native.bbclass: poison TARGET_CFLAGS etc for native builds

[Andre McCurdy <armccurdy@gmail.com>]

TARGET_* FLAGS are never passed to the native toolchain. However,
they are exported so their values affect the checksum of every task.

Replace with fixed values to both avoid any unnecessary rebuilding
of native packages when target flags are changed (as before) and now
also to poison any accidental use of target flags with the native
toolchain.

Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
---
 meta/classes/native.bbclass | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/meta/classes/native.bbclass b/meta/classes/native.bbclass
index f67ef00..34c08b2 100644
--- a/meta/classes/native.bbclass
+++ b/meta/classes/native.bbclass
@@ -26,10 +26,18 @@ TARGET_PREFIX = "${BUILD_PREFIX}"
 TARGET_CC_ARCH = "${BUILD_CC_ARCH}"
 TARGET_LD_ARCH = "${BUILD_LD_ARCH}"
 TARGET_AS_ARCH = "${BUILD_AS_ARCH}"
-TARGET_CPPFLAGS = "${BUILD_CPPFLAGS}"
-TARGET_CFLAGS = "${BUILD_CFLAGS}"
-TARGET_CXXFLAGS = "${BUILD_CXXFLAGS}"
-TARGET_LDFLAGS = "${BUILD_LDFLAGS}"
+
+# TARGET_* FLAGS are never passed to the native toolchain. However, they are
+# exported so their values affect the checksum of every task. Replace with fixed
+# values to both avoid any unnecessary rebuilding of native packages when target
+# flags are changed and to poison any accidental use of target flags with the
+# native toolchain.
+TARGET_CPPFLAGS = "--target-cppflag-never-passed-to-the-native-toolchain"
+TARGET_CFLAGS = "--target-cflag-never-passed-to-the-native-toolchain"
+TARGET_CXXFLAGS = "--target-cxxflag-never-passed-to-the-native-toolchain"
+TARGET_LDFLAGS = "--target-ldflag-never-passed-to-the-native-toolchain"
+
+# Hardcoding is OK since native always implies x86 or x86-64.
 TARGET_FPU = ""
 
 HOST_ARCH = "${BUILD_ARCH}"
-- 
1.9.1