Fix libplacebo/ffmpeg builds on NDKv26

This fixes a confusing error related to Vulkan headers when compiling
libplacebo/ffmpeg - for example in mpv - specifically on Android with
NDK v26. The reason for this is some misplaced Vulkan headers in this
NDK, see android/ndk#1974. But in reality we
should just turn off Vulkan decode support entirely for these libraries
as Google recommends not to use these extensions.

libs/ffmpeg/ffmpeg.py

@@ -171,6 +171,11 @@ def __init__(self, **kwargs):
             if self.subinfo.options.isActive("libs/x265"):
                 self.subinfo.options.configure.args += ["--enable-libx265"]
 
+        if CraftCore.compiler.isAndroid:
+            # Work around https://github.com/android/ndk/issues/1974 in ndk26.
+            # But also Vulkan video decode isn't well supported on Android anyway.
+            self.subinfo.options.configure.args += ["--disable-vulkan"]
+
         if CraftCore.compiler.isMacOS:
             self.subinfo.options.configure.args += ["--enable-rpath", "--install-name-dir=@rpath"]
         elif not CraftCore.compiler.isAndroid:

libs/libplacebo/libplacebo.py

@@ -32,3 +32,8 @@ def __init__(self, **kwargs):
         super().__init__(**kwargs)
         self.subinfo.options.fetch.checkoutSubmodules = True
         self.subinfo.options.configure.args += ["-Ddemos=False"]
+
+        if CraftCore.compiler.isAndroid:
+            # Work around https://github.com/android/ndk/issues/1974 in ndk26.
+            # But also Vulkan video decode isn't well supported on Android anyway.
+            self.subinfo.options.configure.args += ["-Dvulkan=disabled"]