miri core/alloc tests: do not test a 2nd target

Author: RalfJung

src/bootstrap/mk/Makefile.in

@@ -53,15 +53,12 @@ check-aux:
 		src/tools/cargotest \
 		$(BOOTSTRAP_ARGS)
 	# Run standard library tests in Miri.
-	# We use a 64bit little-endian and a 32bit big-endian target for max coverage.
 	$(Q)BOOTSTRAP_SKIP_TARGET_SANITY=1 \
 		$(BOOTSTRAP) miri --stage 2 \
-		--target x86_64-unknown-linux-gnu,mips-unknown-linux-gnu \
 		library/core \
 		library/alloc \
 		--no-doc
 	# Some doctests have intentional memory leaks.
-	# Also, they work only on the host.
 	$(Q)MIRIFLAGS="-Zmiri-ignore-leaks -Zmiri-disable-isolation" \
 		$(BOOTSTRAP) miri --stage 2 \
 		library/core \