Unified sysroot: kill arch-specific include dirs.

<machine/asm.h> was internal use only.

<machine/fenv.h> is quite large, but can live in <bits/...>.

<machine/regdef.h> is trivially replaced by saying $x instead of x in
our assembler.

<machine/setjmp.h> is trivially inlined into <setjmp.h>.

<sgidefs.h> is unused.

Bug: N/A
Test: builds
Change-Id: Id05dbab43a2f9537486efb8f27a5ef167b055815
diff --git a/libc/include/setjmp.h b/libc/include/setjmp.h
index 12a3083..d44946f 100644
--- a/libc/include/setjmp.h
+++ b/libc/include/setjmp.h
@@ -41,11 +41,28 @@
 #define _SETJMP_H_
 
 #include <sys/cdefs.h>
-#include <machine/setjmp.h>
+
+#if defined(__aarch64__)
+#define _JBLEN 32
+#elif defined(__arm__)
+#define _JBLEN 64
+#elif defined(__i386__)
+#define _JBLEN 10
+#elif defined(__mips__)
+  #if defined(__LP64__)
+  #define _JBLEN 25
+  #else
+  #define _JBLEN 157
+  #endif
+#elif defined(__x86_64__)
+#define _JBLEN 11
+#endif
 
 typedef long sigjmp_buf[_JBLEN + 1];
 typedef long jmp_buf[_JBLEN];
 
+#undef _JBLEN
+
 __BEGIN_DECLS
 
 int _setjmp(jmp_buf __env);