Use correct LOCAL_MODULE_TARGET_ARCH for x86_64

valgrind uses amd64 arch name where android build system
uses x86_64. The build file has a substitute for that but
that substitute was mistakenly used for LOCAL_MODULE_TARGET_ARCH
which lead to omitted x86_64 binaries for target builds.

Bug: http://b/30964325
Test: Build aosp_x86_64 and make sure amd64 binaries are present in
Test: out/target/product/generic_x86_64/system/lib64/valgrind/
Change-Id: I6ede1948aaadeea6f01329cd007bcd62e5a4d19f
2 files changed