Make eglfs-egldevice check work with pkgconfig as well

Until now the check didn't use pkgconfig at all, but using pkgconfig
alone does not work for some devices (special cases), so we have to
use a combination of both here.

Change-Id: Ia19a279d80a65352c467661d91a3762448c23ae6
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>

config.tests/qpa/eglfs-egldevice/eglfs-egldevice.pro

@@ -6,7 +6,10 @@ for(p, QMAKE_LIBDIR_EGL) {
 
 INCLUDEPATH += $$QMAKE_INCDIR_EGL
 LIBS += $$QMAKE_LIBS_EGL
-
-LIBS += -ldrm
-
+CONFIG += link_pkgconfig
+!contains(QT_CONFIG, no-pkg-config) {
+    PKGCONFIG += libdrm
+} else {
+    LIBS += -ldrm
+}
 CONFIG -= qt