[MacPorts] #70519: ffmpeg7: does not build on macOS 10.12 with Xcode 9.2 due to "AVMediaType" type conflict

[MacPorts]

#70519: ffmpeg7: does not build on macOS 10.12 with Xcode 9.2 due to "AVMediaType"
type conflict
---------------------+----------------------
 Reporter:  andlabs  |      Owner:  mascguy
     Type:  defect   |     Status:  assigned
 Priority:  Normal   |  Milestone:
Component:  ports    |    Version:
 Keywords:           |       Port:  ffmpeg7
---------------------+----------------------
 Thanks for adding ffmpeg 7! On macOS 10.12 with Xcode 9.2, it fails to
 build with a bunch of confusing errors related to `AVMediaType`:

 {{{
 :info:build libavdevice/avfoundation.m:765:41: error: must use 'enum' tag
 to refer to type 'AVMediaType'
 :info:build static NSArray* getDevicesWithMediaType(AVMediaType mediaType)
 {
 :info:build                                         ^
 :info:build                                         enum
 :info:build libavdevice/avfoundation.m:816:50: warning: incompatible
 integer to pointer conversion sending 'enum AVMediaType' to parameter of
 type 'NSString *' [-Wint-conversion]
 :info:build     return [AVCaptureDevice devicesWithMediaType:mediaType];
 :info:build                                                  ^~~~~~~~~
 :info:build
 /System/Library/Frameworks/AVFoundation.framework/Headers/AVCaptureDevice.h:110:47:
 note: passing argument to parameter 'mediaType' here
 :info:build + (NSArray *)devicesWithMediaType:(NSString *)mediaType;
 :info:build                                               ^
 :info:build libavdevice/avfoundation.m:829:54: warning: incompatible
 pointer to integer conversion passing 'NSString *const' to parameter of
 type 'enum AVMediaType' [-Wint-conversion]
 (snip; see attached log)
 }}}

 I am guessing that the AVFoundation.framework `AVMediaType` was introduced
 in a later version of Xcode's macOS SDK and its lack of presence on my
 headers means ffmpeg defined its own enum with that name?
 [https://trac.macports.org/ticket/65623#comment:27 When I tried building
 ffmpeg 7 a few months ago] I just manually changed the function parameters
 to all be `NSString *` instead; I don't know if that's the correct fix or
 not though, so I'm opening this bug.

-- 
Ticket URL: <https://trac.macports.org/ticket/70519>
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