gfx/dispserv_apple: use RARCH_RELEASE for iv so ARC builds also compile

Fixup for 93cdcb8 ('gfx/dispserv_apple: plug two MRC leaks in
macOS progress/resolution paths').

The previous patch added a raw '[iv release]' inside the
dispatch_once block.  That compiled fine under the top-level qb
Makefile (this file is not in the per-file -fobjc-arc override
list at Makefile:275, so it builds MRC), but every Xcode project
in pkg/apple/ builds it under ARC - pkg/apple/BaseConfig.xcconfig:182
sets CLANG_ENABLE_OBJC_ARC=YES at the target level, and each
Xcode target compiles griffin/griffin_objc.m as a single umbrella
translation unit that #include's dispserv_apple.m (alongside
cocoa_input.m, coreaudio3.m, corelocation.m, and the rest of the
Apple-specific .m sources).  Raw -release is an ARC compile error:

    error: 'release' is unavailable: not available in automatic
    reference counting mode
    error: ARC forbids explicit message send of 'release'

Swap '[iv release]' for 'RARCH_RELEASE(iv)'.  The macro in
libretro-common/include/defines/cocoa_defines.h expands to
'[(x) release]' under MRC (preserving the leak fix from 93cdcb8)
and to '((void)0)' under ARC, where the compiler inserts the
matching release at block-scope exit automatically.  cocoa_defines.h
is already included at line 29 of this file, so no new header is
needed.

Also rewrote the adjacent comment to reflect reality - the file
compiles under BOTH build systems with different ARC modes, not
just MRC as the original comment claimed.  This matches the
build matrix already documented in Makefile:269-276 and
Makefile.common:1649-1665.

Thread-safety / reachability: unchanged from 93cdcb8 - this is
a build-fix only.  Runtime behaviour is identical under qb-MRC
(still does [iv release]) and correct by ARC semantics under
Xcode (ARC auto-releases on block scope exit).

Author: LibretroAdmin

gfx/display_servers/dispserv_apple.m

@@ -84,19 +84,32 @@ static bool apple_display_server_set_window_progress(void *data, int progress, b
       // Create a custom view for the dock tile
       [iv addSubview:indicator];
 
-      /* Under MRC (this file compiles under -fobjc-no-arc per the
-       * top-level Makefile), 'iv' is a local +1 from alloc+init.
-       * setContentView: and addSubview: each retained it for their
-       * own ownership, so at this point its true retain count is
-       * roughly +3.  The two parent-view retains are legitimately
-       * owned; the +1 from alloc+init is ours to release before
-       * the local goes out of scope, or it leaks for the app's
-       * lifetime.  'indicator' is intentionally leaked here - it's
-       * a file-scope static initialised inside dispatch_once, and
-       * holding that +1 across the app lifetime is how we keep it
-       * referenced for the subsequent setDoubleValue / setHidden
-       * calls outside the block. */
-      [iv release];
+      /* This file is compiled under BOTH build systems:
+       *   - qb/top-level Makefile:  MRC (not in the per-file ARC
+       *     override list at Makefile:275 alongside metal.o /
+       *     mfi_joypad.o / coreaudio3.o).
+       *   - pkg/apple/*.xcodeproj:  ARC, via griffin_objc.m which
+       *     #include's this file into a TU compiled with
+       *     CLANG_ENABLE_OBJC_ARC=YES (pkg/apple/BaseConfig.xcconfig:182).
+       *
+       * Under MRC, 'iv' is a local +1 from alloc+init.  setContentView:
+       * and addSubview: each retain their own reference, so those are
+       * legitimately owned; the +1 from alloc+init is ours to release
+       * before the local goes out of scope, or it leaks for the app's
+       * lifetime.  Under ARC, the compiler inserts the matching release
+       * at block scope exit automatically.
+       *
+       * RARCH_RELEASE handles both: MRC -> [(x) release], ARC -> ((void)0).
+       * Raw '[iv release]' is a compile error under ARC
+       * ('ARC forbids explicit message send of release') which the
+       * Xcode build would have flagged immediately.
+       *
+       * 'indicator' is intentionally kept +1 - it's a file-scope static
+       * initialised inside dispatch_once, and holding that +1 across
+       * the app lifetime is how we keep it referenced for the
+       * subsequent setDoubleValue / setHidden calls outside the
+       * block. */
+      RARCH_RELEASE(iv);
    });
    if (finished)
       [indicator setDoubleValue:(double)-1];