Shrink C API release artifacts (#11483)

This is needed to currently shrink our `*.a` artifacts under 100M in
size which is required downstream in the wasmtime-go embedding. Some
testing in #11475 of using full LTO or only building Linux/macOS with 1
CGU shows that this'll likely increase cycle time by ~1 minute. Windows
builders are already the slowest release build builders and this is
adding 1 minute using 1 CGU vs 2-3 extra minutes for full LTO.
Linux/macOS are switched to using full LTO which the CI builders
currently have plenty of time for.

This shaves 50M off the C API artifacts for Linux which buys a good
amount of headroom for future changes.

Closes #11476

Author: alexcrichton

ci/build-release-artifacts.sh

@@ -77,6 +77,21 @@ cargo build --release $flags --target $target -p wasmtime-cli $bin_flags --featu
 # a different project that wants to unwind.
 export RUSTFLAGS="$RUSTFLAGS -C force-unwind-tables"
 
+# Shrink the size of `*.a` artifacts without spending too much extra time in CI.
+# See #11476 for some more context. Here Windows builds achieve this with 1 CGU
+# which results in modest size gains, and other platforms use LTO to achieve
+# much more significant size gains. The reason the platforms are different is
+# that CI is extremely slow on Windows, almost 2x slower, so this is an attempt
+# to keep CI cycle time under control.
+case $build in
+  *-mingw* | *-windows*)
+    export CARGO_PROFILE_RELEASE_CODEGEN_UNITS=1
+    ;;
+  *)
+    export CARGO_PROFILE_RELEASE_LTO=true
+    ;;
+esac
+
 mkdir -p target/c-api-build
 cd target/c-api-build
 cmake \