Use native glib-genmarshal when cross-compiling
Use native glib-genmarshal when cross-compiling

The ability to cross-compile glib got broken after the
merge of the 'signal-performance' branch as the assumption
was made that the generated glib-genmarshal can be executed
on the host (which isn't valid when cross-compiling).

Fixed this by using the just-built glib-genmarshal for normal
compilations and the native (host) glib-genmarshal when doing a
cross-compilation as was also done in several other areas of GLib

Tested for host=x86_64-unknown-linux-gnu, target=x86_64-unknown-linux-gnu
and host=x86_64-unknown-linux-gnu, target=i686-w64-mingw32

https://bugzilla.gnome.org/show_bug.cgi?id=671676

mzabaluev/glib,johne53/MB3Glib,ieei/glib,krichter722/glib,ieei/glib,01org/android-bluez-glib,darren-clark/android_platform_external_bluetooth_glib,tamaskenez/glib,cention-sany/glib,ieei/glib,cention-sany/glib,Distrotech/glib,justinkb/aosp-bluez.glib,MathieuDuponchelle/glib,djdeath/glib,pstglia/platform-external-bluetooth-glib,tchakabam/glib,djdeath/glib,darren-clark/android_platform_external_bluetooth_glib,gale320/glib,bluez-android/glib,mzabaluev/glib,tchakabam/glib,lukasz-skalski/glib,pstglia/external-bluetooth-glib,Distrotech/glib,bluez-android/glib,darren-clark/android_platform_external_bluetooth_glib,tamaskenez/glib,lukasz-skalski/glib,cosimoc/glib,iConsole/Console-OS_external_bluetooth_glib,krichter722/glib,gale320/glib,pstglia/external-bluetooth-glib,lukasz-skalski/glib,johne53/MB3Glib,bluez-android/glib,cosimoc/glib,justinkb/aosp-bluez.glib,pstglia/platform-external-bluetooth-glib,johne53/MB3Glib,iConsole/Console-OS_external_bluetooth_glib,ieei/glib,mzabaluev/glib,MathieuDuponchelle/glib,ieei/glib,justinkb/aosp-bluez.glib,justinkb/aosp-bluez.glib,mzabaluev/glib,gale320/glib,krichter722/glib,endlessm/glib,01org/android-bluez-glib,tamaskenez/glib,darren-clark/android_platform_external_bluetooth_glib,johne53/MB3Glib,Distrotech/glib,johne53/MB3Glib,cosimoc/glib,iConsole/Console-OS_external_bluetooth_glib,iConsole/Console-OS_external_bluetooth_glib,cention-sany/glib,Distrotech/glib,tchakabam/glib,justinkb/aosp-bluez.glib,djdeath/glib,pstglia/platform-external-bluetooth-glib,pstglia/external-bluetooth-glib,gale320/glib,01org/android-bluez-glib,MathieuDuponchelle/glib,iConsole/Console-OS_external_bluetooth_glib,cosimoc/glib,endlessm/glib,MathieuDuponchelle/glib,lukasz-skalski/glib,pstglia/platform-external-bluetooth-glib,endlessm/glib,01org/android-bluez-glib,tamaskenez/glib,pstglia/platform-external-bluetooth-glib,pstglia/external-bluetooth-glib,tchakabam/glib,cention-sany/glib,tchakabam/glib,bluez-android/glib,djdeath/glib,gale320/glib,endlessm/glib,cention-sany/glib,Distrotech/glib,cosimoc/glib,endlessm/glib,MathieuDuponchelle/glib,johne53/MB3Glib,darren-clark/android_platform_external_bluetooth_glib,01org/android-bluez-glib,krichter722/glib,krichter722/glib,mzabaluev/glib,djdeath/glib,bluez-android/glib,lukasz-skalski/glib,pstglia/external-bluetooth-glib,tamaskenez/glib