meson, egl: Support building for the Windows platform

Add a stub EGL driver for Windows
Fix compiler issues in egl/main
Ensure Windows build produces libEGL.dll
Default EGL to enabled for Windows when building a Gallium driver

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed By: Bill Kristiansen <billkris@microsoft.com>

Acked-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12727>

src/egl/main/eglcurrent.c

@@ -33,6 +33,7 @@
 #include "c99_compat.h"
 #include "c11/threads.h"
 #include "util/u_thread.h"
+#include "util/u_string.h"
 
 #include "egllog.h"
 #include "eglcurrent.h"

src/egl/main/egldisplay.c

@@ -35,7 +35,11 @@
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
+#ifdef _WIN32
+#include <io.h>
+#else
 #include <unistd.h>
+#endif
 #include <fcntl.h>
 #include "c11/threads.h"
 #include "util/macros.h"
@@ -77,6 +81,7 @@ static const struct {
    { _EGL_PLATFORM_HAIKU, "haiku" },
    { _EGL_PLATFORM_SURFACELESS, "surfaceless" },
    { _EGL_PLATFORM_DEVICE, "device" },
+   { _EGL_PLATFORM_WINDOWS, "windows" },
 };
 
 

src/egl/main/egldisplay.h

@@ -52,6 +52,7 @@ enum _egl_platform_type {
    _EGL_PLATFORM_HAIKU,
    _EGL_PLATFORM_SURFACELESS,
    _EGL_PLATFORM_DEVICE,
+   _EGL_PLATFORM_WINDOWS,
 
    _EGL_NUM_PLATFORMS,
    _EGL_INVALID_PLATFORM = -1

src/egl/main/eglglobals.c

@@ -39,6 +39,7 @@
 #include "egldisplay.h"
 
 #include "util/macros.h"
+#include "util/os_misc.h"
 
 #ifdef HAVE_MINCORE
 #include <unistd.h>
@@ -137,7 +138,8 @@ EGLBoolean
 _eglPointerIsDereferencable(void *p)
 {
    uintptr_t addr = (uintptr_t) p;
-   const long page_size = getpagesize();
+   uint64_t page_size = 0;
+   os_get_page_size(&page_size);
 #ifdef HAVE_MINCORE
    unsigned char valid = 0;
 

src/egl/main/egllog.c

@@ -39,7 +39,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <strings.h>
 #include "c11/threads.h"
 #include "util/macros.h"
 #include "util/u_string.h"