Since update 5.3.2 -> 5.4.0 Qt5GuiConfigExtras.cmake is unable to find gl(es) header path and fails with
|Failed to find "GLES2/gl2.h" in "/usr/include/libdrm"|
Checking sources leads to:
In configure QMAKE_INCDIR_OPENGL is set with pkg-config. Without
PKG_CONFIG_ALLOW_SYSTEM_CFLAGS set, pkg-config returns paths outside
/usr/include only (in my case /usr/include/libdrm). With NO_DEFAULT_PATH set in Qt5GuiConfigExtras.cmake, gl(es) include directories cannot be found.
The patch attached fixes the bug for me but I have no idea with effects caused to other environments.