build: Use -O0 on Darwin. Seems that Darwin's GCC optimizations break rustrt.

Makefile.in

@@ -11,7 +11,7 @@ endif
 
 CFG_INFO := $(info cfg: building on $(CFG_OSTYPE) $(CFG_CPUTYPE))
 
-CFG_GCC_CFLAGS := -O2 -fno-strict-aliasing
+CFG_GCC_CFLAGS := -fno-strict-aliasing
 CFG_GCC_LINK_FLAGS :=
 CFG_BOOT_FLAGS := $(BOOT_FLAGS)
 CFG_RUSTC_FLAGS := -nowarn -O
@@ -23,7 +23,7 @@ CFG_DSYMUTIL := true
 
 ifeq ($(CFG_OSTYPE), FreeBSD)
   CFG_LIB_NAME=lib$(1).so
-  CFG_GCC_CFLAGS += -fPIC -march=i686 -I/usr/local/include
+  CFG_GCC_CFLAGS += -fPIC -march=i686 -I/usr/local/include -O2
   CFG_GCC_LINK_FLAGS += -shared -fPIC -lpthread -lrt
   ifeq ($(CFG_CPUTYPE), x86_64)
     CFG_GCC_CFLAGS += -m32
@@ -36,7 +36,7 @@ endif
 
 ifeq ($(CFG_OSTYPE), Linux)
   CFG_LIB_NAME=lib$(1).so
-  CFG_GCC_CFLAGS += -fPIC -march=i686
+  CFG_GCC_CFLAGS += -fPIC -march=i686 -O2
   CFG_GCC_LINK_FLAGS += -shared -fPIC -ldl -lpthread -lrt
   CFG_GCC_DEF_FLAG := -Wl,-whole-archive,--export-dynamic,--dynamic-list=
   CFG_GCC_POST_LIB_FLAGS := -Wl,-no-whole-archive
@@ -59,7 +59,9 @@ ifeq ($(CFG_OSTYPE), Darwin)
   # "on an i386" when the whole userspace is 64-bit and the compiler
   # emits 64-bit binaries by default. So we just force -m32 here. Smarter
   # approaches welcome!
-  CFG_GCC_CFLAGS += -m32
+  #
+  # NB: Currently GCC's optimizer breaks rustrt (task-comm-1 hangs) on Darwin.
+  CFG_GCC_CFLAGS += -m32 -O0
   CFG_GCC_LINK_FLAGS += -m32
   CFG_DSYMUTIL := dsymutil
   CFG_DEF_SUFFIX := .darwin.def
@@ -90,7 +92,7 @@ ifdef CFG_WINDOWSY
   ifdef CFG_FLEXLINK
     CFG_BOOT_NATIVE := 1
   endif
-  CFG_GCC_CFLAGS += -march=i686
+  CFG_GCC_CFLAGS += -march=i686 -O2
   CFG_GCC_LINK_FLAGS += -shared -fPIC
   CFG_DEF_SUFFIX := .def
 endif