Bug 31646: Update abicheck to require GLIBCXX_3.4.25

This is also fixing bug 31380.

projects/firefox/abicheck.cc

 /*
  * Bug 25485: Browser/TorBrowser/Tor/libstdc++.so.6: version `CXXABI_1.3.11' not found
- * This program is borrowed from
- * https://en.cppreference.com/w/cpp/error/uncaught_exception and is useful in
- * determining the latest C++ ABI. Specifically this program requires
- * `GLIBCXX_3.4.22` which we use to compare the version of the installed
- * libstdc++.so.6 and the bundled version. If the program executes
- * successfully, that means we should use the system version of libstdc++.so.6
- * and if not, that means we should use the bundled version.
+ * Bug 31646: Update abicheck to require newer libstdc++.so.6
+ * This program is useful in determining if the libstdc++.so.6 installed
+ * on the system is recent enough. Specifically this program requires
+ * `GLIBCXX_3.4.25` which should be provided by libstdc++.so.6 from
+ * gcc >= 8.0.0. If the program executes successfully, that means we
+ * should use the system version of libstdc++.so.6 and if not, that means
+ * we should use the bundled version.
+ *
+ * We use std::random_device::entropy() in order to require GLIBCXX_3.4.25:
+ * https://github.com/gcc-mirror/gcc/blob/gcc-8_3_0-release/libstdc%2B%2B-v3/config/abi/pre/gnu.ver#L1978
  */
 
 #include <iostream>
-#include <exception>
-#include <stdexcept>
-
-struct Foo {
-    int count = std::uncaught_exceptions();
-    ~Foo() {
-        std::cout << (count == std::uncaught_exceptions()
-            ? "~Foo() called normally\n"
-            : "~Foo() called during stack unwinding\n");
-    }
-};
+#include <random>
 
 int main()
 {
-    Foo f;
-    try {
-        Foo f;
-        std::cout << "Exception thrown\n";
-        throw std::runtime_error("test exception");
-    } catch (const std::exception& e) {
-        std::cout << "Exception caught: " << e.what() << '\n';
-    }
+    std::random_device rd;
+    std::cout << "entropy: " << rd.entropy() << std::endl;
+    return 0;
 }

projects/gcc/config

 # vim: filetype=yaml sw=2
 filename: '[% project %]-[% c("version") %]-[% c("var/build_id") %].tar.gz'
+# Note: When updating the gcc version, if this includes a libstdc++
+# ABI change we should also update projects/firefox/abicheck.cc to
+# require the new version.
 version: 8.3.0
 var:
   container: