plumbing to automatically run MIR for crates where it works;

this serves as a poor man's unit test infrastructure until
MIR is more built up

mk/main.mk

@@ -172,6 +172,18 @@ RUST_LIB_FLAGS_ST3 += -C prefer-dynamic
 # by not emitting them.
 RUSTFLAGS_STAGE0 += -Z no-landing-pads
 
+# Enable MIR to "always build" for crates where this works. This is
+# just temporary while MIR is being actively built up -- it's just a
+# poor man's unit testing infrastructure. Anyway we only want this for
+# stage1/stage2.
+define ADD_MIR_FLAG
+RUSTFLAGS1_$(1) += -Z always-build-mir
+RUSTFLAGS2_$(1) += -Z always-build-mir
+endef
+$(foreach crate,$(TARGET_CRATES),$(eval $(call ADD_MIR_FLAG,$(crate))))
+$(foreach crate,$(RUSTC_CRATES),$(eval $(call ADD_MIR_FLAG,$(crate))))
+$(foreach crate,syntax,$(eval $(call ADD_MIR_FLAG,$(crate))))
+
 # platform-specific auto-configuration
 include $(CFG_SRC_DIR)mk/platform.mk
 

mk/target.mk

@@ -93,6 +93,7 @@ $$(TLIB$(1)_T_$(2)_H_$(3))/stamp.$(4): \
 		$$(LLVM_LIBDIR_RUSTFLAGS_$(2)) \
 		$$(LLVM_STDCPP_RUSTFLAGS_$(2)) \
 		$$(RUSTFLAGS_$(4)) \
+		$$(RUSTFLAGS$(1)_$(4)) \
 		$$(RUSTFLAGS$(1)_$(4)_T_$(2)) \
 		--out-dir $$(@D) \
 		-C extra-filename=-$$(CFG_FILENAME_EXTRA) \