Avoid inheriting PRIVATE_BOOTCLASSPATH from moduels that depend on api-stubs-timestamp
Avoid inheriting PRIVATE_BOOTCLASSPATH from moduels that depend on api-stubs-timestamp

The inherited value has caused build breakage on Mac build.

Change-Id: I8a1b1d6c6d411f6aaaee2d8dbd0297e3d60ab5c2

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