Add a --multiarch-triplet switch to configure

Add a --multiarch-triplet switch to configure. The switch will allow
files to be search for each default path in path/<triplet> and then
path.
Default paths handled that way:
- CONFIG_TCC_SYSINCLUDE_PATHS
- CONFIG_TCC_LIBPATH
- path to crt*.o
- path to libgcc_s.so.1

Path missing: elf interpreter path (will be handled in another commit)

tccelf.c

@@ -1238,7 +1238,10 @@ ST_FUNC void tcc_add_runtime(TCCState *s1)
     if (!s1->nostdlib) {
 #ifdef CONFIG_USE_LIBGCC
         tcc_add_library(s1, "c");
-        tcc_add_file(s1, CONFIG_SYSROOT CONFIG_TCC_LDDIR"/libgcc_s.so.1");
+#ifdef CONFIG_TCC_MULTIARCH_TRIPLET
+        if (tcc_add_file_internal(s1, CONFIG_SYSROOT CONFIG_TCC_LDDIR "/" CONFIG_TCC_MULTIARCH_TRIPLET "/libgcc_s.so.1", 0))
+#endif
+            tcc_add_file(s1, CONFIG_SYSROOT CONFIG_TCC_LDDIR"/libgcc_s.so.1");
 #else
         tcc_add_library(s1, "c");
 #ifndef WITHOUT_LIBTCC
@@ -1252,7 +1255,10 @@ ST_FUNC void tcc_add_runtime(TCCState *s1)
     }
     /* add crt end if not memory output */
     if (s1->output_type != TCC_OUTPUT_MEMORY && !s1->nostdlib) {
-        tcc_add_file(s1, CONFIG_SYSROOT CONFIG_TCC_CRT_PREFIX "/crtn.o");
+#ifdef CONFIG_TCC_MULTIARCH_TRIPLET
+        if (tcc_add_file_internal(s1, CONFIG_SYSROOT CONFIG_TCC_CRT_PREFIX "/" CONFIG_TCC_MULTIARCH_TRIPLET "/crtn.o", 0))
+#endif
+            tcc_add_file(s1, CONFIG_SYSROOT CONFIG_TCC_CRT_PREFIX "/crtn.o");
     }
 }