[GTK] REGRESSION(255909@main): GBM dependency may be disabled by mistake

https://bugs.webkit.org/show_bug.cgi?id=247132

Reviewed by Žan Doberšek.

Add a new USE_GBM option tied to the USE_OPENGL_OR_ES option. Unless
this option is disabled, GBM and libdrm and mandatory. This ensures that
dmabuf support does get disabled by mistake.

Importantly, note the dmabuf enablement no longer depends on ENABLE_WEBGL.

* Source/cmake/OptionsGTK.cmake:

Canonical link: https://commits.webkit.org/256152@main

Source/cmake/OptionsGTK.cmake

@@ -66,6 +66,7 @@ WEBKIT_OPTION_DEFINE(ENABLE_QUARTZ_TARGET "Whether to enable support for the Qua
 WEBKIT_OPTION_DEFINE(ENABLE_WAYLAND_TARGET "Whether to enable support for the Wayland windowing target." PUBLIC ON)
 WEBKIT_OPTION_DEFINE(ENABLE_X11_TARGET "Whether to enable support for the X11 windowing target." PUBLIC ON)
 WEBKIT_OPTION_DEFINE(USE_AVIF "Whether to enable support for AVIF images." PUBLIC ON)
+WEBKIT_OPTION_DEFINE(USE_GBM "Whether to enable usage of GBM and libdrm." PUBLIC ON)
 WEBKIT_OPTION_DEFINE(USE_GTK4 "Whether to enable usage of GTK4 instead of GTK3." PUBLIC OFF)
 WEBKIT_OPTION_DEFINE(USE_JPEGXL "Whether to enable support for JPEG-XL images." PUBLIC ${ENABLE_EXPERIMENTAL_FEATURES})
 WEBKIT_OPTION_DEFINE(USE_LCMS "Whether to enable support for image color management using libcms2." PUBLIC ON)
@@ -84,6 +85,7 @@ WEBKIT_OPTION_DEPEND(ENABLE_3D_TRANSFORMS USE_OPENGL_OR_ES)
 WEBKIT_OPTION_DEPEND(ENABLE_ASYNC_SCROLLING USE_OPENGL_OR_ES)
 WEBKIT_OPTION_DEPEND(ENABLE_GLES2 USE_OPENGL_OR_ES)
 WEBKIT_OPTION_DEPEND(ENABLE_WEBGL USE_OPENGL_OR_ES)
+WEBKIT_OPTION_DEPEND(USE_GBM USE_OPENGL_OR_ES)
 WEBKIT_OPTION_DEPEND(USE_GSTREAMER_GL USE_OPENGL_OR_ES)
 
 WEBKIT_OPTION_CONFLICT(USE_GTK4 USE_SOUP2)
@@ -387,17 +389,23 @@ if (USE_OPENGL_OR_ES)
     SET_AND_EXPOSE_TO_BUILD(USE_NICOSIA TRUE)
     SET_AND_EXPOSE_TO_BUILD(USE_ANGLE ${ENABLE_WEBGL})
 
-    if (ENABLE_WEBGL)
+    if (USE_GBM)
         # ANGLE-backed WebGL depends on DMABuf support, which at the moment is leveraged
-        # through libgbm and libdrm dependencies. When libgbm is found to be available,
-        # make libdrm a requirement and define the USE_LIBGBM and USE_TEXTURE_MAPPER_DMABUF
+        # through libgbm and libdrm dependencies. When libgbm is enabled, make
+        # libdrm a requirement and define the USE_LIBGBM and USE_TEXTURE_MAPPER_DMABUF
         # macros. When not available, ANGLE will be used in slower software-rasterization mode.
         find_package(GBM)
-        if (GBM_FOUND)
-            find_package(LibDRM REQUIRED)
-            SET_AND_EXPOSE_TO_BUILD(USE_LIBGBM TRUE)
-            SET_AND_EXPOSE_TO_BUILD(USE_TEXTURE_MAPPER_DMABUF TRUE)
+        if (NOT GBM_FOUND)
+            message(FATAL_ERROR "GBM is required for USE_GBM")
         endif ()
+
+        find_package(LibDRM)
+        if (NOT LIBDRM_FOUND)
+            message(FATAL_ERROR "libdrm is required for USE_GBM")
+        endif ()
+
+        SET_AND_EXPOSE_TO_BUILD(USE_LIBGBM TRUE)
+        SET_AND_EXPOSE_TO_BUILD(USE_TEXTURE_MAPPER_DMABUF TRUE)
     endif ()
 endif ()