rust: Do not use default compiler flags defined in CC crate

Rust crates build dependecy C libraries using "CC" crate.
This crate adds some default compiler parameters depending on target arch.
For some targets these parameters conflict with the parameters defined by OE.

Warnings/errors like this can be seen in the case:

cc1: error: switch '-mcpu=cortex-a15' conflicts with switch '-march=armv7-a+fp' [-Werror]

Lets use only the OE parameters by exporting CRATE_CC_NO_DEFAULTS.
https://github.com/rust-lang/cc-rs#external-configuration-via-environment-variables

This patch fixes https://bugzilla.yoctoproject.org/show_bug.cgi?id=14947

(From OE-Core rev: 0c07089bdf7e0d7d8f37552db0bcd75f860979d9)

Signed-off-by: Anton Antonov <Anton.Antonov@arm.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/meta/classes-recipe/rust-target-config.bbclass b/meta/classes-recipe/rust-target-config.bbclass
index 7fd7128bcf..939dd13d2f 100644
--- a/meta/classes-recipe/rust-target-config.bbclass
+++ b/meta/classes-recipe/rust-target-config.bbclass
@@ -404,3 +404,19 @@ python do_rust_gen_targets () {
 addtask rust_gen_targets after do_patch before do_compile
 do_rust_gen_targets[dirs] += "${RUST_TARGETS_DIR}"
 
+# For building target C dependecies use only compiler parameters defined in OE
+# and ignore the CC crate defaults which conflicts with OE ones in some cases.
+# https://github.com/rust-lang/cc-rs#external-configuration-via-environment-variables
+# Some CC crate compiler flags are still required.
+# We apply them conditionally in rust wrappers.
+
+CRATE_CC_FLAGS:class-native = ""
+CRATE_CC_FLAGS:class-nativesdk = ""
+CRATE_CC_FLAGS:class-target = " -ffunction-sections -fdata-sections -fPIC"
+
+do_compile:prepend:class-target() {
+    export CRATE_CC_NO_DEFAULTS=1
+}
+do_install:prepend:class-target() {
+    export CRATE_CC_NO_DEFAULTS=1
+}