make compiler profile to use stage0 on x check

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Author: onur-ozkan

src/bootstrap/defaults/bootstrap.compiler.toml

@@ -1,5 +1,7 @@
 # These defaults are meant for contributors to the compiler who do not modify codegen or LLVM
 [build]
+# Enforce stage0 to avoid checking stage1 std which requires to build stage1 compiler.
+check-stage = 0
 # Contributors working on the compiler will probably expect compiler docs to be generated.
 compiler-docs = true