build: remove unnecessary pragmas

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5629055

include/plan9/libc.h

@@ -10,9 +10,6 @@ enum
 	Runemax = 0x10FFFF, /* maximum rune value */
 };
 
-#pragma src "/sys/src/go/src/lib9"
-#pragma lib "/sys/src/go/lib/$M/lib9.a"
-
 char*	getgoos(void);
 char*	getgoarch(void);
 char*	getgoroot(void);

include/plan9/mach.h

@@ -2,6 +2,4 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-#pragma src "/sys/src/go/src/libmach"
-#pragma lib "/sys/src/go/lib/$M/libmach.a"
 #include "../mach.h"

src/cmd/cc/cc.h

@@ -31,8 +31,6 @@
 #include <libc.h>
 #include <bio.h>
 
-#pragma	lib	"../cc/cc.a$O"
-
 #ifndef	EXTERN
 #define EXTERN	extern
 #endif

src/cmd/gc/go.h

@@ -4,8 +4,6 @@
 
 #include	<bio.h>
 
-#pragma	lib	"../gc/gc.a$O"
-
 #undef OAPPEND
 
 // avoid <ctype.h>