Don't enable dtrace support when dtrace isn't available
Don't enable dtrace support when dtrace isn't available

Fixes FTBFS when dtrace isn't available but <sys/sdt.h> is.

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