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

libc/runtime/ftrace-hook.S

@@ -68,14 +68,15 @@ ftrace_hook:
 
 #elif defined(__aarch64__)
 
-	adrp	x16,__ftrace
-	ldr	w16,[x16,#:lo12:__ftrace]
-	cmp	w16,0
-	ble	1f
 	stp	x29,x30,[sp,-384]!
 	mov	x29,sp
-
 	stp	x0,x1,[sp,16]
+
+	adrp	x0,__ftrace
+	ldr	w0,[x0,#:lo12:__ftrace]
+	cmp	w0,0
+	ble	1f
+
 	stp	x2,x3,[sp,32]
 	stp	x4,x5,[sp,48]
 	stp	x6,x7,[sp,64]
@@ -83,12 +84,12 @@ ftrace_hook:
 	stp	x10,x11,[sp,96]
 	stp	x12,x13,[sp,112]
 	stp	x14,x15,[sp,128]
-	str	x19,[sp,160]
+	stp	x16,x19,[sp,160]
 	stp	x20,x21,[sp,176]
 	stp	x22,x23,[sp,192]
 	stp	x24,x25,[sp,208]
 	stp	x26,x27,[sp,224]
-	str	x28,[sp,240]
+	stp	x17,x28,[sp,240]
 	stp	q0,q1,[sp,256]
 	stp	q2,q3,[sp,288]
 	stp	q4,q5,[sp,320]
@@ -96,27 +97,27 @@ ftrace_hook:
 
 	bl	ftracer
 
-	ldp	x0,x1,[sp,16]
-	ldp	x2,x3,[sp,32]
-	ldp	x4,x5,[sp,48]
-	ldp	x6,x7,[sp,64]
-	ldp	x8,x9,[sp,80]
-	ldp	x10,x11,[sp,96]
-	ldp	x12,x13,[sp,112]
-	ldp	x14,x15,[sp,128]
-	ldr	x19,[sp,160]
-	ldp	x20,x21,[sp,176]
-	ldp	x22,x23,[sp,192]
-	ldp	x24,x25,[sp,208]
-	ldp	x26,x27,[sp,224]
-	ldr	x28,[sp,240]
-	ldp	q0,q1,[sp,256]
-	ldp	q2,q3,[sp,288]
-	ldp	q4,q5,[sp,320]
 	ldp	q6,q7,[sp,352]
+	ldp	q4,q5,[sp,320]
+	ldp	q2,q3,[sp,288]
+	ldp	q0,q1,[sp,256]
+	ldp	x17,x28,[sp,240]
+	ldp	x26,x27,[sp,224]
+	ldp	x24,x25,[sp,208]
+	ldp	x22,x23,[sp,192]
+	ldp	x20,x21,[sp,176]
+	ldp	x16,x19,[sp,160]
+	ldp	x14,x15,[sp,128]
+	ldp	x12,x13,[sp,112]
+	ldp	x10,x11,[sp,96]
+	ldp	x8,x9,[sp,80]
+	ldp	x6,x7,[sp,64]
+	ldp	x4,x5,[sp,48]
+	ldp	x2,x3,[sp,32]
 
+1:	ldp	x0,x1,[sp,16]
 	ldp	x29,x30,[sp],384
-1:	ret
+	ret
 
 #endif /* __x86_64__ */
 	.endfn	ftrace_hook,globl,hidden