[arm] amend stack pointer properly in exception trampoline (mono/mono…

…#14310)

The previous attempt ( mono/mono#14078 ) only fixed it for ABIs where the stack pointer alignment is 8 bytes. ABIs, such as watchOS, require 16 byte alignment.

Commit migrated from mono/mono@1cbd5cb

src/mono/mono/mini/exceptions-arm.c

@@ -252,7 +252,8 @@ get_throw_trampoline (int size, gboolean corlib, gboolean rethrow, gboolean llvm
 	int param_size = 8;
 	if (!resume_unwind && !corlib)
 		param_size += 4; // Extra arg
-	param_size = ALIGN_TO (param_size, MONO_ARCH_FRAME_ALIGNMENT);
+	/* SP isn't 16byte aligned at this point which matters for some targets */
+	param_size = ALIGN_TO (cfa_offset + param_size, MONO_ARCH_FRAME_ALIGNMENT) - cfa_offset;
 	ARM_SUB_REG_IMM8 (code, ARMREG_SP, ARMREG_SP, param_size);
 	cfa_offset += param_size;
 	mono_add_unwind_op_def_cfa_offset (unwind_ops, code, start, cfa_offset);