Add support for m68k (#900)

Fixes #895

absl/base/internal/direct_mmap.h

@@ -74,6 +74,7 @@ namespace base_internal {
 inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
                         off64_t offset) noexcept {
 #if defined(__i386__) || defined(__ARM_ARCH_3__) || defined(__ARM_EABI__) || \
+    defined(__m68k__) ||                                                     \
     (defined(__mips__) && _MIPS_SIM == _MIPS_SIM_ABI32) ||                   \
     (defined(__PPC__) && !defined(__PPC64__)) ||                             \
     (defined(__riscv) && __riscv_xlen == 32) ||                              \

absl/debugging/internal/examine_stack.cc

@@ -51,6 +51,8 @@ void* GetProgramCounter(void* vuc) {
 #elif defined(__i386__)
     if (14 < ABSL_ARRAYSIZE(context->uc_mcontext.gregs))
       return reinterpret_cast<void*>(context->uc_mcontext.gregs[14]);
+#elif defined(__m68k__)
+    return reinterpret_cast<void*>(context->uc_mcontext.gregs[16]);
 #elif defined(__mips__)
     return reinterpret_cast<void*>(context->uc_mcontext.pc);
 #elif defined(__powerpc64__)