Add missing X11 extension headers.

This patch modifies the set of packages used to build the toolchain
sysroot to include libxext-dev, which is required to provide certain
headers like <X11/extensions/XShm.h> required to build the emulator's
SDL sources.

+ Ensure the environment is properly sanitized when building the
  toolchain.

Change-Id: I219d647bae8e71b353b5973261150f4bb6656501
diff --git a/sysroot/usr/include/X11/extensions/XShm.h b/sysroot/usr/include/X11/extensions/XShm.h
new file mode 100644
index 0000000..b58ca63
--- /dev/null
+++ b/sysroot/usr/include/X11/extensions/XShm.h
@@ -0,0 +1,136 @@
+/* $XFree86: xc/include/extensions/XShm.h,v 1.11 2003/04/03 15:11:07 dawes Exp $ */
+/************************************************************
+
+Copyright 1989, 1998  The Open Group
+
+Permission to use, copy, modify, distribute, and sell this software and its
+documentation for any purpose is hereby granted without fee, provided that
+the above copyright notice appear in all copies and that both that
+copyright notice and this permission notice appear in supporting
+documentation.
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+Except as contained in this notice, the name of The Open Group shall not be
+used in advertising or otherwise to promote the sale, use or other dealings
+in this Software without prior written authorization from The Open Group.
+
+********************************************************/
+
+/* THIS IS NOT AN X CONSORTIUM STANDARD OR AN X PROJECT TEAM SPECIFICATION */
+
+/* $Xorg: XShm.h,v 1.4 2001/02/09 02:03:24 xorgcvs Exp $ */
+
+#ifndef _XSHM_H_
+#define _XSHM_H_
+
+#include <X11/Xfuncproto.h>
+#include <X11/extensions/shm.h>
+
+typedef unsigned long ShmSeg;
+
+typedef struct {
+    int	type;		    /* of event */
+    unsigned long serial;   /* # of last request processed by server */
+    Bool send_event;	    /* true if this came frome a SendEvent request */
+    Display *display;	    /* Display the event was read from */
+    Drawable drawable;	    /* drawable of request */
+    int major_code;	    /* ShmReqCode */
+    int minor_code;	    /* X_ShmPutImage */
+    ShmSeg shmseg;	    /* the ShmSeg used in the request */
+    unsigned long offset;   /* the offset into ShmSeg used in the request */
+} XShmCompletionEvent;
+
+typedef struct {
+    ShmSeg shmseg;	/* resource id */
+    int shmid;		/* kernel id */
+    char *shmaddr;	/* address in client */
+    Bool readOnly;	/* how the server should attach it */
+} XShmSegmentInfo;
+
+_XFUNCPROTOBEGIN
+
+Bool XShmQueryExtension(
+    Display*		/* dpy */
+);
+
+int XShmGetEventBase(
+    Display* 		/* dpy */
+);
+
+Bool XShmQueryVersion(
+    Display*		/* dpy */,
+    int*		/* majorVersion */,
+    int*		/* minorVersion */,
+    Bool*		/* sharedPixmaps */
+);
+
+int XShmPixmapFormat(
+    Display*		/* dpy */
+);
+
+Status XShmAttach(
+    Display*		/* dpy */,
+    XShmSegmentInfo*	/* shminfo */
+);
+
+Status XShmDetach(
+    Display*		/* dpy */,
+    XShmSegmentInfo*	/* shminfo */
+);
+
+Status XShmPutImage(
+    Display*		/* dpy */,
+    Drawable		/* d */,
+    GC			/* gc */,
+    XImage*		/* image */,
+    int			/* src_x */,
+    int			/* src_y */,
+    int			/* dst_x */,
+    int			/* dst_y */,
+    unsigned int	/* src_width */,
+    unsigned int	/* src_height */,
+    Bool		/* send_event */
+);
+
+Status XShmGetImage(
+    Display*		/* dpy */,
+    Drawable		/* d */,
+    XImage*		/* image */,
+    int			/* x */,
+    int			/* y */,
+    unsigned long	/* plane_mask */
+);
+
+XImage *XShmCreateImage(
+    Display*		/* dpy */,
+    Visual*		/* visual */,
+    unsigned int	/* depth */,
+    int			/* format */,
+    char*		/* data */,
+    XShmSegmentInfo*	/* shminfo */,
+    unsigned int	/* width */,
+    unsigned int	/* height */
+);
+
+Pixmap XShmCreatePixmap(
+    Display*		/* dpy */,
+    Drawable		/* d */,
+    char*		/* data */,
+    XShmSegmentInfo*	/* shminfo */,
+    unsigned int	/* width */,
+    unsigned int	/* height */,
+    unsigned int	/* depth */
+);
+
+_XFUNCPROTOEND
+
+#endif