use ignore directives for run-make tests

This makes the tests easier to read, and makes it possible to tell which
tests aren't being run on the host platform.

Fixes #56704.

Author: euclio

src/test/run-make-fulldeps/c-dynamic-dylib/Makefile

@@ -1,14 +1,12 @@
 -include ../tools.mk
 
+# ignore-macos
+#
 # This hits an assertion in the linker on older versions of osx apparently
-ifeq ($(shell uname),Darwin)
-all:
-	echo ignored
-else
+
 all: $(call DYLIB,cfoo)
 	$(RUSTC) foo.rs -C prefer-dynamic
 	$(RUSTC) bar.rs
 	$(call RUN,bar)
 	$(call REMOVE_DYLIBS,cfoo)
 	$(call FAIL,bar)
-endif

src/test/run-make-fulldeps/c-dynamic-rlib/Makefile

@@ -1,17 +1,15 @@
 -include ../tools.mk
 
+# ignore-macos
+#
+# This hits an assertion in the linker on older versions of osx apparently
+
 # This overrides the LD_LIBRARY_PATH for RUN
 TARGET_RPATH_DIR:=$(TARGET_RPATH_DIR):$(TMPDIR)
 
-# This hits an assertion in the linker on older versions of osx apparently
-ifeq ($(shell uname),Darwin)
-all:
-	echo ignored
-else
 all: $(call DYLIB,cfoo)
 	$(RUSTC) foo.rs
 	$(RUSTC) bar.rs
 	$(call RUN,bar)
 	$(call REMOVE_DYLIBS,cfoo)
 	$(call FAIL,bar)
-endif