zig build: change "-Drelease" to "-Doptimize"

I find myself quite often creating ReleaseSafe builds and putting them
to production for certain experiments:
- Debug info are for stack traces. An ongoing example where those would
  help is ziglang#14815.
- Safety checks would have saved a couple of mine and @kubkon's hours in
  ziglang#15098.

This is a breaking change for scripts that make Zig releases -- I will
submit another PR to zig-bootstrap and release-cutter after this is
merged.

CMakeLists.txt

@@ -810,9 +810,9 @@ endif()
 if("${CMAKE_BUILD_TYPE}" STREQUAL "Debug")
   set(ZIG_RELEASE_ARG "")
 elseif("${CMAKE_BUILD_TYPE}" STREQUAL "RelWithDebInfo")
-  set(ZIG_RELEASE_ARG -Drelease)
+  set(ZIG_RELEASE_ARG -Doptimize=ReleaseFast)
 else()
-  set(ZIG_RELEASE_ARG -Drelease -Dstrip)
+  set(ZIG_RELEASE_ARG -Doptimize=ReleaseFast -Dstrip)
 endif()
 if(ZIG_NO_LIB)
   set(ZIG_NO_LIB_ARG "-Dno-lib")

build.zig

@@ -13,7 +13,6 @@ const zig_version = std.builtin.Version{ .major = 0, .minor = 11, .patch = 0 };
 const stack_size = 32 * 1024 * 1024;
 
 pub fn build(b: *std.Build) !void {
-    const release = b.option(bool, "release", "Build in release mode") orelse false;
     const only_c = b.option(bool, "only-c", "Translate the Zig compiler to C code, with only the C backend enabled") orelse false;
     const target = t: {
         var default_target: std.zig.CrossTarget = .{};
@@ -22,10 +21,10 @@ pub fn build(b: *std.Build) !void {
         }
         break :t b.standardTargetOptions(.{ .default_target = default_target });
     };
-    const optimize: std.builtin.OptimizeMode = if (release) switch (target.getCpuArch()) {
-        .wasm32 => .ReleaseSmall,
-        else => .ReleaseFast,
-    } else .Debug;
+
+    // TODO remove type annotation with ziglang/zig#13749
+    const optimize: std.builtin.Mode = b.option(std.builtin.Mode, "optimize", "Prioritize performance, safety, or binary size (-O flag)") orelse
+        if (target.getCpuArch() == .wasm32) .ReleaseSmall else .Debug;
 
     const single_threaded = b.option(bool, "single-threaded", "Build artifacts that run in single threaded mode");
     const use_zig_libcxx = b.option(bool, "use-zig-libcxx", "If libc++ is needed, use zig's bundled version, don't try to integrate with the system") orelse false;

ci/aarch64-macos.sh

@@ -58,7 +58,7 @@ stage3-release/bin/zig build \
   --prefix stage4-release \
   -Denable-llvm \
   -Dno-lib \
-  -Drelease \
+  -Doptimize=ReleaseFast \
   -Dstrip \
   -Dtarget=$TARGET \
   -Duse-zig-libcxx \

ci/x86_64-linux-release.sh

@@ -77,7 +77,7 @@ stage3-release/bin/zig build \
   --prefix stage4-release \
   -Denable-llvm \
   -Dno-lib \
-  -Drelease \
+  -Doptimize=ReleaseFast \
   -Dstrip \
   -Dtarget=$TARGET \
   -Duse-zig-libcxx \

ci/x86_64-macos-release.sh

@@ -62,7 +62,7 @@ stage3/bin/zig build \
   --prefix stage4 \
   -Denable-llvm \
   -Dno-lib \
-  -Drelease \
+  -Doptimize=ReleaseFast \
   -Dstrip \
   -Dtarget=$TARGET \
   -Duse-zig-libcxx \