Clarify a few comments

Python/jit.c

@@ -409,8 +409,11 @@ _PyJIT_Compile(_PyExecutorObject *executor, const _PyUOpInstruction *trace, size
     unsigned char *code = memory;
     unsigned char *data = memory + code_size;
     {
-        // Compile the trampoline, which handles changing the calling convention
-        // (on platforms where it's not necessary, the trampoline is empty):
+        // Compile the trampoline, which handles converting between the native
+        // calling convention and the calling convention used by jitted code
+        // (which may be different for efficiency reasons). On platforms where
+        // we don't change calling conventions, the trampoline is empty and
+        // nothing is emitted here:
         const StencilGroup *group = &trampoline;
         // Think of patches as a dictionary mapping HoleValue to uintptr_t:
         uintptr_t patches[] = GET_PATCHES();

Tools/jit/_targets.py

@@ -480,6 +480,7 @@ def _handle_relocation(
 
 def get_target(host: str) -> _COFF | _ELF | _MachO:
     """Build a _Target for the given host "triple" and options."""
+    # ghccc currently crashes Clang when combined with musttail on aarch64. :(
     if re.fullmatch(r"aarch64-apple-darwin.*", host):
         return _MachO(host, alignment=8, prefix="_")
     if re.fullmatch(r"aarch64-pc-windows-msvc", host):