UPSTREAM: arm64: compat: vdso: Expose BUILD_VDSO32

clock_gettime32 and clock_getres_time32 should be compiled only with the
32 bit vdso library.

Expose BUILD_VDSO32 when arm64 compat is compiled, to provide an
indication to the generic library to include these symbols.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20190830135902.20861-2-vincenzo.frascino@arm.com


(cherry picked from commit 3b5584afeef05319ade0fbf5f634a64fd3e5772b)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 154668398
Change-Id: Ie4f5b438ef48a41b3f61e4868e5727176dcdb464