Fix rustdoc-scrape-examples-macros test not being cross-platform

Author: willcrichton

src/test/run-make-fulldeps/rustdoc-scrape-examples-macros/Makefile

@@ -1,14 +1,15 @@
 -include ../../run-make-fulldeps/tools.mk
 
 OUTPUT_DIR := "$(TMPDIR)/rustdoc"
+DYLIB_NAME := $(shell echo | $(RUSTC) --crate-name foobar_macro --crate-type dylib --print file-names -)
 
 all:
 	$(RUSTC) src/proc.rs --crate-name foobar_macro --edition=2021 --crate-type proc-macro --emit=dep-info,link
 
 	$(RUSTC) src/lib.rs --crate-name foobar --edition=2021 --crate-type lib --emit=dep-info,link
 
 	$(RUSTDOC) examples/ex.rs --crate-name ex --crate-type bin --output $(OUTPUT_DIR) \
-		--extern foobar=$(TMPDIR)/libfoobar.rlib --extern foobar_macro=$(TMPDIR)/libfoobar_macro.so \
+		--extern foobar=$(TMPDIR)/libfoobar.rlib --extern foobar_macro=$(TMPDIR)/$(DYLIB_NAME) \
 		-Z unstable-options --scrape-examples-output-path $(TMPDIR)/ex.calls --scrape-examples-target-crate foobar
 
 	$(RUSTDOC) src/lib.rs --crate-name foobar --crate-type lib --output $(OUTPUT_DIR) \