Don't assume dlsym exists on linux

After checking if -ldl exists, use it for checking for the dlsym
function.

This fixes building in environments where the dlsym function is
unavailable. (My testcase is NDK builds with -static, where dlsym
isn't available for static linking, only if linking dynamically.)

meson.build

@@ -136,6 +136,9 @@ endif
 libdl_dependency = []
 if host_machine.system() == 'linux'
     libdl_dependency = cc.find_library('dl', required : false)
+    if cc.has_function('dlsym', prefix : '#include <dlfcn.h>', args : test_args, dependencies : libdl_dependency)
+        cdata.set('HAVE_DLSYM', 1)
+    endif
 endif
 
 

src/lib.c

@@ -99,7 +99,7 @@ COLD int dav1d_open(Dav1dContext **const c_out, const Dav1dSettings *const s) {
     pthread_attr_t thread_attr;
     if (pthread_attr_init(&thread_attr)) return DAV1D_ERR(ENOMEM);
     size_t stack_size = 1024 * 1024;
-#ifdef __linux__
+#if defined(__linux__) && defined(HAVE_DLSYM)
     /* glibc has an issue where the size of the TLS is subtracted from the stack
      * size instead of allocated separately. As a result the specified stack
      * size may be insufficient when used in an application with large amounts