build: bump max_rss of std lib tests to 5G

Author: andrewrk

build.zig

@@ -513,8 +513,8 @@ pub fn build(b: *std.Build) !void {
         .skip_non_native = skip_non_native,
         .skip_libc = skip_libc,
         .use_llvm = use_llvm,
-        // I observed a value of 4572626944 on the M2 CI.
-        .max_rss = 5029889638,
+        // I observed a value of 5136793600 on the M2 CI.
+        .max_rss = 5368709120,
     }));
 
     const unit_tests_step = b.step("test-unit", "Run the compiler source unit tests");