graphics/pcl-pointclouds: fix build on powerpc64 with clang

lld on powerpc64 elfv2 can't link this port, add LLD_UNSAFE=yes:
ld: error: relocation refers to a discarded section: .text.__clang_call_terminate

defined in common/CMakeFiles/pcl_common.dir/src/pcl_base.cpp.o
section group signature: __clang_call_terminate
prevailing definition is in common/CMakeFiles/pcl_common.dir/src/point_types.cpp.o
referenced by pcl_base.cpp

common/CMakeFiles/pcl_common.dir/src/pcl_base.cpp.o:(pcl::PCLBase<pcl::PCLPointCloud2>::initCompute())

PR: 241944
Approved by: mentors (implicit approval), yuri (maintainer timeout)