Disable -Wunused-macros under GCC Since the pragram in hb-ot-shape-complex-indic-table.cc didn't seem to silence GCC, eg: ../../src/hb-ot-shape-complex-indic-table.cc:55: warning: macro "ISC_TL" is not used [-Wunused-macros] 55 | #define ISC_TL INDIC_SYLLABIC_CATEGORY_TONE_LETTER /* 7 chars; Tone_Letter */ disable it at compiler level.