x11/pixman: fix build on armv7

 - due to a regression in some binutils>2.40 version, the assembly code
   no longer assembles.  Remove leading zeros from local labels to fix
   this.
 - the arm64 assembly code has some other issue which appears to have
   been fixed upstream in 0.43.0, so don't bother with that; PR 276296
   will address this.

See also:	https://gitlab.freedesktop.org/pixman/pixman/-/issues/96
MFH:		2024Q4

(cherry picked from commit b751d107)