run-make: Specify --target to rustc

Resolves #78911

The target's linker was used but rustc wasn't told to build for that
target (instead defaulting to the host). This led to the host instead of
the target getting tested and to the linker getting inappropriate
arguments.

Author: tblah

src/test/run-make/incr-prev-body-beyond-eof/Makefile

@@ -1,8 +1,5 @@
 include ../../run-make-fulldeps/tools.mk
 
-# FIXME https://github.com/rust-lang/rust/issues/78911
-# ignore-32bit wrong/no cross compiler and sometimes we pass wrong gcc args (-m64)
-
 # Tests that we don't ICE during incremental compilation after modifying a
 # function span such that its previous end line exceeds the number of lines
 # in the new file, but its start line/column and length remain the same.
@@ -14,6 +11,6 @@ all:
 	mkdir $(SRC)
 	mkdir $(INCR)
 	cp a.rs $(SRC)/main.rs
-	$(RUSTC) -C incremental=$(INCR) $(SRC)/main.rs
+	$(RUSTC) -C incremental=$(INCR) $(SRC)/main.rs --target $(TARGET)
 	cp b.rs $(SRC)/main.rs
-	$(RUSTC) -C incremental=$(INCR) $(SRC)/main.rs
+	$(RUSTC) -C incremental=$(INCR) $(SRC)/main.rs --target $(TARGET)

src/test/run-make/issue-36710/Makefile

@@ -1,13 +1,10 @@
 include ../../run-make-fulldeps/tools.mk
 
-# FIXME https://github.com/rust-lang/rust/issues/78911
-# ignore-32bit wrong/no cross compiler and sometimes we pass wrong gcc args (-m64)
-
 all: foo
 	$(call RUN,foo)
 
 foo: foo.rs $(call NATIVE_STATICLIB,foo)
-	$(RUSTC) $< -lfoo $(EXTRARSCXXFLAGS)
+	$(RUSTC) $< -lfoo $(EXTRARSCXXFLAGS) --target $(TARGET)
 
 $(TMPDIR)/libfoo.o: foo.cpp
 	$(call COMPILE_OBJ_CXX,$@,$<)

src/test/run-make/issue-83112-incr-test-moved-file/Makefile

@@ -1,8 +1,5 @@
 include ../../run-make-fulldeps/tools.mk
 
-# FIXME https://github.com/rust-lang/rust/issues/78911
-# ignore-32bit wrong/no cross compiler and sometimes we pass wrong gcc args (-m64)
-
 # Regression test for issue #83112
 # The generated test harness code contains spans with a dummy location,
 # but a non-dummy SyntaxContext. Previously, the incremental cache was encoding
@@ -20,6 +17,6 @@ all:
 	mkdir $(SRC)/mydir
 	mkdir $(INCR)
 	cp main.rs $(SRC)/main.rs
-	$(RUSTC) --test -C incremental=$(INCR) $(SRC)/main.rs
+	$(RUSTC) --test -C incremental=$(INCR) $(SRC)/main.rs --target $(TARGET)
 	mv $(SRC)/main.rs $(SRC)/mydir/main.rs
-	$(RUSTC) --test -C incremental=$(INCR) $(SRC)/mydir/main.rs
+	$(RUSTC) --test -C incremental=$(INCR) $(SRC)/mydir/main.rs --target $(TARGET)