perf(mobile): stop iOS syntax highlighting from looking up a thread-local on every lexer call

Compiled as C11, the wasm2c runtime makes its stack depth counter thread-local, and on Apple platforms every lexer function entry then calls _tlv_get_addr. The pod's C files now compile as gnu99, where wasm2c falls back to a plain global on Apple. Callers already serialize the lexer, so the counter never needs per-thread state.

Author: camchis

apps/mobile/modules/t3-highlights/T3HighlightsNative.podspec

@@ -20,6 +20,10 @@ Pod::Spec.new do |s|
   s.compiler_flags = '-O2'
   s.pod_target_xcconfig = {
     'DEFINES_MODULE' => 'YES',
+    # Under C11, wasm2c makes its stack depth counter thread-local, so every lexer
+    # function entry calls _tlv_get_addr (2–9% of lexing time on an iPhone 12).
+    # Callers already serialize the lexer (t3_highlights.h), so a plain global is safe.
+    'GCC_C_LANGUAGE_STANDARD' => 'gnu99',
     # Plain malloc memory with explicit bounds checks: no guard-page signal
     # handlers competing with the app's crash reporting.
     'GCC_PREPROCESSOR_DEFINITIONS' => '$(inherited) WASM_RT_USE_MMAP=0 WASM_RT_MEMCHECK_BOUNDS_CHECK=1 WASM_RT_SKIP_SIGNAL_RECOVERY=1',