Add fix for winpthreads breakage

A regression in winpthreads is causing `libvpx` to fails. Until the fix
reaches the `msys2` packages, apply the fix ourselves.

Author: jlaine

.github/workflows/build-ffmpeg.yml

@@ -54,7 +54,7 @@ jobs:
         run: |
           brew update
           brew unlink gettext libidn2 libpng libtiff libunistring libx11 libxau libxcb libxdmcp little-cms2 unbound
-      - uses: msys2/setup-msys2@c52d1fa9c7492275e60fe763540fb601f5f232a1
+      - uses: msys2/setup-msys2@v2
         if: matrix.os == 'windows-latest'
         with:
           install: base-devel mingw-w64-x86_64-gcc mingw-w64-x86_64-gperf mingw-w64-x86_64-nasm openssl-devel

patches/winpthreads.patch

@@ -0,0 +1,26 @@
+Temporary patch for this issue:
+
+https://sourceforge.net/p/mingw-w64/mailman/message/59184409/
+
+This patch can be removed once msys2's packages have been updated.
+
+--- a/mingw-w64-libraries/winpthreads/include/pthread_time.h
++++ b/mingw-w64-libraries/winpthreads/include/pthread_time.h
+@@ -23,6 +23,7 @@
+ #ifndef WIN_PTHREADS_TIME_H
+ #define WIN_PTHREADS_TIME_H
+ 
++#include <sys/timeb.h>
+ #include "pthread_compat.h"
+ 
+ /* Posix timers are supported */
+--- a/mingw-w64-libraries/winpthreads/include/semaphore.h
++++ b/mingw-w64-libraries/winpthreads/include/semaphore.h
+@@ -23,6 +23,7 @@
+ #ifndef WIN_PTHREADS_SEMAPHORE_H
+ #define WIN_PTHREADS_SEMAPHORE_H
+ 
++#include <sys/timeb.h>
+ #include "pthread_compat.h"
+ 
+ #ifdef __cplusplus

scripts/build-ffmpeg.py

@@ -335,6 +335,10 @@ def main():
     builder = Builder(dest_dir=dest_dir)
     builder.create_directories()
 
+    # Fix winpthreads breakage until the fix reaches msys2 repos.
+    if plat == "Windows":
+        run(["patch", "-d", "C:/msys64/mingw64", "-i", os.path.join(builder.patch_dir, "winpthreads.patch"), "-p3"])
+
     # install packages
     available_tools = set()
     if plat == "Windows":