Fix generic build on Max OS X 10.7 Lion
Fix generic build on Max OS X 10.7 Lion

    Recover variable build_mac_version which is removed on
    commit 644dc16 and added on commit 9ce06f1.

    Without this, ranlib libSDL.a is executed on Lion which
    causes build fail of emulator-arm.

Change-Id: I06144a288921f8f968ef457999398c1b9152d4aa

see4ri/lolili,xorware/android_build,RR-msm7x30/platform_manifest,fallouttester/platform_manifest,xorware/android_build,xorware/android_build,hagar006/platform_manifest,pranav01/platform_manifest,xorware/android_build,Hybrid-Power/startsync,xorware/android_build,ND-3500/platform_manifest,knone1/platform_manifest