build: Don't fail for 32 bit builds because of static_assert check (AcademySoftwareFoundation#4006)

A static_assert was added recently as part of PR AcademySoftwareFoundation#3898, which assures
that the size of a TileID is a multiple of 8 bytes. But on architectures
with 32 bit pointers, this assertion fails. Which is not quite what we
want, because the code isn't wrong if the struct isn't a multiple of 8
bytes; it's just less efficient. And we don't want to fail for 32 bit
arch.

Bottom line: only do this check to ensure we're in the most efficient
case if we're 64 bits. Nobody's expecting highest performance on a 32
bit machine anyway.

Fixes AcademySoftwareFoundation#4001

Signed-off-by: Larry Gritz <[email protected]>

Author: lgritz

src/libtexture/imagecache_pvt.h

@@ -567,9 +567,11 @@ struct TileID {
         static_assert(
             sizeof(*this) == member_size,
             "All TileID members must be accounted for so we can hash the entire class.");
+#ifdef __LP64__
         static_assert(
             sizeof(*this) % sizeof(uint64_t) == 0,
             "FastHash uses the fewest instructions when data size is a multiple of 8 bytes.");
+#endif
         return fasthash::fasthash64(this, sizeof(*this));
     }