Use libtcc.a for static link even with USE_LIBGCC

When statically linking, runtime library should be static as well. tcc
could link with libgcc.a but it's in a gcc version specific directory.
Another solution, followed by this patch, is to use libtcc.a when
statically linking, even if USE_LIBGCC was configured.

configure

@@ -273,7 +273,7 @@ Advanced options (experts only):
   --strip-binaries         strip symbol tables from resulting binaries
   --disable-static         make libtcc.so instead of libtcc.a
   --disable-rpath          disable use of -rpath with the above
-  --with-libgcc            use /lib/libgcc_s.so.1 instead of libtcc.a
+  --with-libgcc            use libgcc_s.so.1 instead of libtcc.a in dynamic link
   --enable-mingw32         build windows version on linux with mingw32
   --enable-cygwin          build windows version on windows with cygwin
   --enable-cross           build cross compilers

tccelf.c

@@ -1363,7 +1363,12 @@ ST_FUNC void tcc_add_runtime(TCCState *s1)
     if (!s1->nostdlib) {
         tcc_add_library(s1, "c");
 #ifdef CONFIG_USE_LIBGCC
-        tcc_add_file(s1, TCC_LIBGCC);
+        if (!s1->static_link)
+            tcc_add_file(s1, TCC_LIBGCC);
+#if !defined WITHOUT_LIBTCC
+        else
+            tcc_add_support(s1, "libtcc1.a");
+#endif
 #elif !defined WITHOUT_LIBTCC
         tcc_add_support(s1, "libtcc1.a");
 #endif