package/libdrm: fix install of test programs

Buildroot commit f95069814bd68cfc10ccf2dbc41efa6f1e127495 disabled the
build of test programs unconditionally without considering the option
BR2_PACKAGE_LIBDRM_INSTALL_TESTS.

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 91848e73ae6f5ad6ca0568f8e7309247379e51f1)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libdrm/libdrm.mk

@@ -17,8 +17,7 @@ LIBDRM_DEPENDENCIES = \
 
 LIBDRM_CONF_OPTS = \
 	-Dcairo-tests=disabled \
-	-Dman-pages=disabled \
-	-Dtests=false
+	-Dman-pages=disabled
 
 ifeq ($(BR2_PACKAGE_LIBATOMIC_OPS),y)
 LIBDRM_DEPENDENCIES += libatomic_ops
@@ -109,10 +108,12 @@ LIBDRM_CONF_OPTS += -Dvalgrind=disabled
 endif
 
 ifeq ($(BR2_PACKAGE_LIBDRM_INSTALL_TESTS),y)
-LIBDRM_CONF_OPTS += -Dinstall-test-programs=true
+LIBDRM_CONF_OPTS += -Dtests=true -Dinstall-test-programs=true
 ifeq ($(BR2_PACKAGE_CUNIT),y)
 LIBDRM_DEPENDENCIES += cunit
 endif
+else
+LIBDRM_CONF_OPTS += -Dtests=false
 endif
 
 $(eval $(meson-package))