fix(aur): append -fuse-ld=bfd to RUSTFLAGS — substitution was no-op on CachyOS

makepkg.conf on Arch injects -fuse-ld=lld into RUSTFLAGS which overrides
.cargo/config.toml target rustflags. PKGBUILD now explicitly patches
RUSTFLAGS at env level so bfd is used regardless of system config.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.cargo/config.toml

@@ -3,6 +3,10 @@
 # resolve (ring_core_* symbols). Fix: force cc as linker driver and append
 # -fuse-ld=bfd so it overrides the hardcoded -fuse-ld=lld (last flag wins).
 # bfd is always available via binutils (part of base-devel on Arch).
+#
+# NOTE: When building via makepkg (AUR), RUSTFLAGS from /etc/makepkg.conf
+# overrides target-specific rustflags here. The PKGBUILD's build() applies
+# the same fix by patching the RUSTFLAGS env var directly.
 [target.x86_64-unknown-linux-gnu]
 linker = "cc"
 rustflags = ["-C", "link-arg=-fuse-ld=bfd"]

packages/aur/PKGBUILD

@@ -27,6 +27,13 @@ build() {
   export CARGO_HOME="$srcdir/cargo-home"
   export npm_config_cache="$srcdir/npm-cache"
 
+  # ring (used by tauri-plugin-updater → rustls) ships C/asm objects whose
+  # symbols (ring_core_*) lld cannot resolve.  On Arch/CachyOS, -fuse-ld=lld
+  # is hardcoded into rustc itself (not just makepkg.conf RUSTFLAGS), so a
+  # string substitution is a no-op.  Appending -C link-arg=-fuse-ld=bfd works
+  # because the last -fuse-ld=* flag passed to cc wins.
+  export RUSTFLAGS="${RUSTFLAGS} -C link-arg=-fuse-ld=bfd"
+
   npm install
   npm run tauri:build -- --no-bundle
 }