x11/pixman: mark as LLD_UNSAFE

/usr/bin/ld: error: can't create dynamic relocation R_ARM_V4BX against local symbol in readonly segment; recompile object files with -fPIC

defined in ./.libs/libpixman-arm-simd.a(pixman-arm-simd-asm-scaled.o)
referenced by pixman-arm-simd-asm-scaled.o:(.text+0x1B8) in archive ./.libs/libpixman-arm-simd.a

PR: 233740
Reported by: Charlie Li
Approved by: portmgr blanket