databases/mysql57-server: don't use LLD for linking on powerpc

LLD currently fails:
ld: error: relocation refers to a discarded section: .rodata._ZN5boost6detail8function15functor_managerINS_9algorithm6detail13token_finderFINS4_10is_any_ofFIcEEEEE7managerERKNS1_15function_bufferERSA_NS1_30functor_manager_operation_typeEN4mpl_5bool_ILb0EEE

defined in ../../archive_output_directory/libmysqlpump_lib.a(object_filter.cc.o)
referenced by object_filter.cc

object_filter.cc.o:(.got2+0x108) in archive ../../archive_output_directory/libmysqlpump_lib.a

ld: error: relocation refers to a discarded section: .rodata._ZN5boost6detail8function15functor_managerINS_9algorithm6detail13token_finderFINS4_10is_any_ofFIcEEEEE7managerERKNS1_15function_bufferERSA_NS1_30functor_manager_operation_typeEN4mpl_5bool_ILb0EEE

defined in ../../archive_output_directory/libmysqlpump_lib.a(sql_formatter.cc.o)
referenced by sql_formatter.cc

sql_formatter.cc.o:(.got2+0x130) in archive ../../archive_output_directory/libmysqlpump_lib.a

ld: error: relocation refers to a discarded section: .rodata._ZN5boost6detail8function15functor_managerINS_9algorithm6detail13token_finderFINS4_10is_any_ofFIcEEEEE7managerERKNS1_15function_bufferERSA_NS1_30functor_manager_operation_typeEN4mpl_5bool_ILb0EEE

defined in ../../archive_output_directory/libmysqlpump_lib.a(table.cc.o)
referenced by table.cc

table.cc.o:(.got2+0x50) in archive ../../archive_output_directory/libmysqlpump_lib.a

clang++: error: linker command failed with exit code 1 (use -v to see invocation)