package/libglib2: fix building on older distributions

package/libglib2: fix building on older distributions

When updating to libglib2 2.62.0, the file 0002-add-option-to-build-tests.patch
had to be refactored to work with the new build_tests checks. In the process of
refactoring, a missing check was overlooked in glib/meson.build causing
distributions with older versions of objcopy to fail because the older version
does not contain the --add-symbol argument.

Adding the check for the build_tests argument fixes the issue.

Fixes:
http://autobuild.buildroot.net/results/dcc2352a036aba9650eae8abaaa23819fc67332d

Signed-off-by: Adam Duskett <Aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>