glsl: fix a memory leak with resource_set

glsl: fix a memory leak with resource_set

   ==7265== 248 (120 direct, 128 indirect) bytes in 1 blocks are definitely lost in loss record 1,438 of 1,465
   ==7265==    at 0x483980B: malloc (vg_replace_malloc.c:309)
   ==7265==    by 0x598A2AB: ralloc_size (ralloc.c:119)
   ==7265==    by 0x598F861: _mesa_set_create (set.c:127)
   ==7265==    by 0x599079D: _mesa_pointer_set_create (set.c:570)
   ==7265==    by 0x58BD7D1: build_program_resource_list(gl_context*, gl_shader_program*, bool) (linker.cpp:4026)
   ==7265==    by 0x548231B: st_link_shader (st_glsl_to_ir.cpp:170)
   ==7265==    by 0x54DA269: _mesa_glsl_link_shader (ir_to_mesa.cpp:3119)

Fixes: a6aedc66 ("st/glsl_to_nir: use nir based program resource list builder")
Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3574>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3574>