auto merge of #16373 : brson/rust/nopads, r=pcwalton

Reduces time to build stage0 from 11:30 to 9:40 on my machine.

There's a tradeoff here since doing this will make the stage1 compile-fail tests fail.

r? @pcwalton

Author: bors

mk/main.mk

@@ -139,6 +139,10 @@ endif
 RUSTFLAGS_STAGE0 += -C prefer-dynamic
 RUSTFLAGS_STAGE1 += -C prefer-dynamic
 
+# Landing pads require a lot of codegen. We can get through bootstrapping faster
+# by not emitting them.
+RUSTFLAGS_STAGE0 += -Z no-landing-pads
+
 # platform-specific auto-configuration
 include $(CFG_SRC_DIR)mk/platform.mk