Bug 1610986 - add a specific target for lucet compilation; r=firefox-build-system-reviewers,rstewart

We're going to need this for handling Mac cross compiles correctly.

Depends on D62795

Differential Revision: https://phabricator.services.mozilla.com/D62796

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

config/rules.mk

@@ -566,6 +566,7 @@ $(WASM_ARCHIVE): $(CWASMOBJS) $(CPPWASMOBJS) $(STATIC_LIBS) $(EXTRA_DEPS) $(GLOB
 	$(WASM_CXX) $(OUTOPTION)$@ -Wl,--export-all $(WASM_LDFLAGS) $(CWASMOBJS) $(CPPWASMOBJS)
 
 lucet_options := \
+    --target $(LUCETC_TARGET) \
     --target-cpu baseline \
     --bindings $(topsrcdir)/third_party/rust/lucet-wasi/bindings.json \
     --guard-size 4GiB \

toolkit/moz.configure

@@ -1890,6 +1890,10 @@ with only_when(requires_wasm_sandboxing & compile_environment):
             return value
     set_config('WASM_LDFLAGS', wasm_ldflags)
 
+    # Re-using the Rust target triple here is not exactly correct, but it is an
+    # excellent approximation for the platforms we currently support
+    set_config('LUCETC_TARGET', rust_target_triple)
+
 
 @depends('--with-wasm-sandboxed-libraries', target)
 def wasm_sandboxing(libraries, target):