No need to override mkshrc as it no longer exports PS1

busybox sh works fine with the one in android_external_mksh

Change-Id: I09ae2d16837053ea0be50d3320eccf47057e25c1
Merge remote-tracking branch 'cm/cm-10.2' into cm-10.2
Merge remote-tracking branch 'androidarmv6/cm-10.2' into cm-10.2