Update #38335 with main.

Bring drexin's FreeBSD support patch up to date with main. Resolved
conflicts in prior merge commit and made some minor buildfixes. Still
requires some other more general fixes outside this pr to have this build
properly at HEAD but have verified only this builds OK with those fixes
possibly TK including #59987 on FreeBSD 12.3.

Note: I don't intend to support this platform as a priority.

Author: 3405691582

lib/Threading/Pthreads.cpp

@@ -101,6 +101,7 @@ swift::threading_impl::thread_get_current_stack_bounds() {
 #if defined(__FreeBSD__)
   if (pthread_attr_init(&attr))
     return {};
+#define pthread_getattr_np pthread_attr_get_np
 #endif
 
   if (!pthread_getattr_np(pthread_self(), &attr)) {

stdlib/public/CommandLineSupport/CommandLine.cpp

@@ -36,6 +36,8 @@
 #include <shellapi.h>
 #endif
 
+#include <errno.h>
+
 // Backing storage for overrides of `Swift.CommandLine.arguments`.
 static char **_swift_stdlib_ProcessOverrideUnsafeArgv = nullptr;
 static int _swift_stdlib_ProcessOverrideUnsafeArgc = 0;