Make improvements

- You can now run `make -j8 toolchain` on Windows
- You can now run `make -j` on MacOS ARM64 and BSD OSes
- You can now use our Emacs dev environment on MacOS/Windows
- Fix bug where the x16 register was being corrupted by --ftrace
- The programs under build/bootstrap/ are updated as fat binaries
- The Makefile now explains how to download cosmocc-0.0.12 toolchain
- The build scripts under bin/ now support "cosmo" branded toolchains
- stat() now goes faster on Windows (shaves 100ms off `make` latency)
- Code cleanup and added review on the Windows signal checking code
- posix_spawnattr_setrlimit() now works around MacOS ARM64 bugs
- Landlock Make now favors posix_spawn() on non-Linux/OpenBSD
- posix_spawn() now has better --strace logging on Windows
- fstatat() can now avoid EACCES in more cases on Windows
- fchmod() can now change the readonly bit on Windows

build/config.mk

@@ -16,6 +16,12 @@ CONFIG_CCFLAGS += -O2 $(BACKTRACES)
 CONFIG_CPPFLAGS += -DSYSDEBUG
 TARGET_ARCH ?= -msse3
 endif
+ifeq ($(MODE), x86_64)
+ENABLE_FTRACE = 1
+CONFIG_OFLAGS ?= -g
+CONFIG_CCFLAGS += -O2 $(BACKTRACES)
+CONFIG_CPPFLAGS += -DSYSDEBUG
+endif
 ifeq ($(MODE), aarch64)
 ENABLE_FTRACE = 1
 CONFIG_OFLAGS ?= -g
@@ -39,8 +45,8 @@ CONFIG_CPPFLAGS += -DSYSDEBUG
 endif
 ifeq ($(MODE), aarch64-zero)
 CONFIG_OFLAGS ?= -g
-OVERRIDE_CFLAGS += -O0
-OVERRIDE_CXXFLAGS += -O0
+OVERRIDE_CFLAGS += -O0 -fdce
+OVERRIDE_CXXFLAGS += -O0 -fdce
 CONFIG_CPPFLAGS += -DSYSDEBUG
 endif
 
@@ -166,7 +172,7 @@ ifeq ($(MODE), aarch64-dbg)
 ENABLE_FTRACE = 1
 CONFIG_OFLAGS ?= -g
 CONFIG_CPPFLAGS += -DMODE_DBG -D__SANITIZE_UNDEFINED__
-CONFIG_CCFLAGS += $(BACKTRACES) -DSYSDEBUG -O0 -fno-inline
+CONFIG_CCFLAGS += $(BACKTRACES) -DSYSDEBUG -O0 -fno-inline -fdce
 CONFIG_COPTS += -fsanitize=undefined
 QUOTA ?= -C64 -L300
 endif