Fix LTO with secp256k1's C code.

diff --git a/genbindings.sh b/genbindings.sh
index 7a876312ae2cc818533225ca81326e8f48adc526..8fd11889910401d21b01cbd6d81393a36ef34495 100755 (executable)
--- a/genbindings.sh
+++ b/genbindings.sh
@@ -271,7 +271,11 @@ if [ "$HOST_PLATFORM" != "host: x86_64-apple-darwin" -a "$CLANGPP" != "" ]; then
        # or Ubuntu packages). This should work fine on Distros which do more involved
        # packaging than simply shipping the rustup binaries (eg Debian should Just Work
        # here).
-       export CFLAGS="$CFLAGS -flto"
+       # The cc-rs crate tries to force -fdata-sections and -ffunction-sections on, which
+       # breaks -fembed-bitcode, so we turn off cc-rs' default flags and specify exactly
+       # what we want here.
+       export CFLAGS="$CFLAGS -O3 -fPIC -fembed-bitcode"
+       export CRATE_CC_NO_DEFAULTS=true
        # Rust doesn't recognize CFLAGS changes, so we need to clean build artifacts
        cargo clean --release
        CARGO_PROFILE_RELEASE_LTO=true cargo rustc -v --release -- -C linker-plugin-lto -C lto -C link-arg=-fuse-ld=lld