CI: add coverage for fuzzer compiling

From mlugg: this commit originally also added the same coverage to the
aarch64-linux-release script, but that caused the aarch64-linux-release
job to time out, so that change has been omitted for now.

ci/aarch64-macos-release.sh

@@ -51,6 +51,10 @@ stage3-release/bin/zig build test docs \
   --search-prefix "$PREFIX" \
   --test-timeout 2m
 
+# Ensure that the fuzzer at least compiles.
+stage3-release/bin/zig build test-std --fuzz=1K -Dno-lib -Dfuzz-only -Doptimize=ReleaseSafe
+stage3-release/bin/zig build test-std --fuzz=1K -Dno-lib -Dfuzz-only -Doptimize=Debug
+
 # Ensure that stage3 and stage4 are byte-for-byte identical.
 stage3-release/bin/zig build \
   --maxrss ${ZSF_MAX_RSS:-0} \

ci/x86_64-linux-release.sh

@@ -51,7 +51,10 @@ unset CXX
 
 ninja install
 
-# simultaneously test building self-hosted without LLVM and with 32-bit arm
+# Covers several things:
+# 1. building the compiler without LLVM
+# 2. 32-bit
+# 3. arm
 stage3-release/bin/zig build \
   -Dtarget=arm-linux-musleabihf \
   -Dno-lib
@@ -70,6 +73,10 @@ stage3-release/bin/zig build test docs \
   -Denable-superhtml \
   --test-timeout 12m
 
+# Ensure that the fuzzer at least compiles.
+stage3-release/bin/zig build test-std --fuzz=1K -Dno-lib -Dfuzz-only -Doptimize=ReleaseSafe
+stage3-release/bin/zig build test-std --fuzz=1K -Dno-lib -Dfuzz-only -Doptimize=Debug
+
 # Ensure that stage3 and stage4 are byte-for-byte identical.
 stage3-release/bin/zig build \
   --prefix stage4-release \

ci/x86_64-windows-release.ps1

@@ -54,6 +54,13 @@ stage3-release\bin\zig.exe build test docs `
   --test-timeout 30m
 CheckLastExitCode
 
+# Ensure that the fuzzer at least compiles.
+# https://codeberg.org/ziglang/zig/issues/31893
+# stage3-release\bin\zig.exe build test-std --fuzz=1K -Dno-lib -Dfuzz-only -Doptimize=ReleaseSafe
+# CheckLastExitCode
+# stage3-release\bin\zig.exe build test-std --fuzz=1K -Dno-lib -Dfuzz-only -Doptimize=Debug
+# CheckLastExitCode
+
 # Ensure that stage3 and stage4 are byte-for-byte identical.
 Write-Output "Build and compare stage4..."
 stage3-release\bin\zig.exe build `