8145547 breaks AIX and and uses RTLD_NOLOAD incorrectly

Change 8145547 uses the RTLD_NOLOAD flag when calling dlopen to probe the availability of the GTK libraries.

But unfortunately RTLD_NOLOAD is not Posix and for example not available on AIX and BSD.

I also found out, that the implementation of 8145547 contains a bug. It uses RTLD_NOLOAD in an incorrect way. The man page for dlopen clearly states that one of the two flags RTLD_LAZY or RTLD_NOW has to be included in the flags. But the current implementation uses RTLD_NOLOAD as single flag. Therefor the call to dlopen() currently always returns NULL, no difference if the corresponding library has been loaded already or not.

The following short C program demonstrates the problem:

#include <dlfcn.h>
#include <stdio.h>

int main(int argc, char **argv) {

  void* l = dlopen("libgtk-x11-2.0.so.0", RTLD_LAZY | RTLD_LOCAL);
  fprintf(stderr, "l = %p\n", l);

  dlerror();
  l = dlopen("libgtk-x11-2.0.so.0", RTLD_NOLOAD);
  fprintf(stderr, "l = %p (error = %s)\n", l, dlerror());

  l = dlopen("libgtk-x11-2.0.so.0", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
  fprintf(stderr, "l = %p\n", l);

}

It will print:

l = 0x10033f81c50
l = (nil) (error = libgtk-x11-2.0.so.0: invalid mode for dlopen(): Invalid argument)
l = 0x10033f81c50