Bug 1541068 - add Rust compilation directories to GARBAGE_DIRS; r=nalexander

We add to `GARBAGE_DIRS` in the toplevel `Makefile.in` because all of
our Rust libraries share a single `CARGO_TARGET_DIR`, located in
topobjdir.

We add to `GARBAGE_DIRS` for Rust programs because Rust programs
currently do not share compilation artifacts with Rust libraries (as our
libraries are built with `panic=abort` and our programs are not, sharing
compilation artifacts between the two is a non-starter).

Differential Revision: https://phabricator.services.mozilla.com/D26762

--HG--
extra : moz-landing-system : lando

Makefile.in

@@ -24,6 +24,13 @@ endif
 include $(topsrcdir)/config/config.mk
 
 GARBAGE_DIRS += _javagen _profile staticlib
+# To share compilation of dependencies, Rust libraries all set their
+# CARGO_TARGET_DIR as a subdirectory of topobjdir.  Normally, we would add
+# RUST*TARGET to GARBAGE_DIRS for those directories building Rust libraries.
+# But the directories building Rust libraries don't actually have
+# subdirectories to remove.  So we add to GARBAGE_DIRS once here, globally,
+# for it to have the desired effect.
+GARBAGE_DIRS += $(RUST_TARGET)
 DIST_GARBAGE = config.cache config.log config.status* config-defs.h \
    config/autoconf.mk \
    mozilla-config.h \

config/makefiles/rust.mk

@@ -290,6 +290,9 @@ force-cargo-host-library-check:
 endif # HOST_RUST_LIBRARY_FILE
 
 ifdef RUST_PROGRAMS
+
+GARBAGE_DIRS += $(RUST_TARGET)
+
 force-cargo-program-build:
 	$(REPORT_BUILD)
 	$(call CARGO_BUILD) $(addprefix --bin ,$(RUST_CARGO_PROGRAMS)) $(cargo_target_flag)
@@ -303,6 +306,9 @@ force-cargo-program-check:
 	@true
 endif # RUST_PROGRAMS
 ifdef HOST_RUST_PROGRAMS
+
+GARBAGE_DIRS += $(RUST_HOST_TARGET)
+
 force-cargo-host-program-build:
 	$(REPORT_BUILD)
 	$(call CARGO_BUILD) $(addprefix --bin ,$(HOST_RUST_CARGO_PROGRAMS)) $(cargo_host_flag)