jni_generator: Fix header guard

When generating header guards for source files under sandboxed
directories, the path component "/.temp/" may be included, and the
period character is not allowed by Clang for a token after #ifndef.

error: extra tokens at end of #ifndef directive [-Werror,-Wextra-tokens]
#ifndef _SRV_ADELVA_SOONG_.TEMP_SBOX_BDF5053FBDC997EA57..
                          ^
                          //

Change-Id: Ifb6dd30eaa3c4fb13591c5f520024baa2bbf378d
1 file changed