mediafoundation: Test compile steps v/s step , and set build flag

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/work_items/15244
Backport-to: *

Reviewed-by: Pohsiang (John) Hsu <pohhsu@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41221>
(cherry picked from commit c5b184a02a)

.pick_status.json

@@ -3174,7 +3174,7 @@
         "description": "mediafoundation: Test compile steps v/s step , and set build flag",
         "nominated": true,
         "nomination_type": 4,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null,
         "notes": null

src/gallium/frontends/mediafoundation/codecapi.cpp

@@ -958,7 +958,11 @@ CDX12EncHMFT::GetValue( const GUID *Api, VARIANT *Value )
       hevcDeltaQPSettings.dataType = CODEC_API_QP_MAP_INT8;
       hevcDeltaQPSettings.minValue = static_cast<INT16>( m_uiMinQP );
       hevcDeltaQPSettings.maxValue = static_cast<INT16>( m_uiMaxQP );
+#if defined(INPUTQPSETTINGS_HAS_STEPS)
+      hevcDeltaQPSettings.steps = 1;
+#else
       hevcDeltaQPSettings.step = 1;
+#endif
 
       SAFEARRAYBOUND bound = { static_cast<ULONG>( sizeof( hevcDeltaQPSettings ) ),
                                static_cast<LONG>( 0 ) };       // cElements , lower bound

src/gallium/frontends/mediafoundation/meson.build

@@ -47,6 +47,35 @@ if get_option('mediafoundation-store-dll')
   mf_cpp_args += '-DBUILD_FOR_MSDK' # Can use #if BUILD_FOR_MSDK in .cpp code
 endif
 
+# InputQPSettings::step was renamed to ::steps in BR (Bromine) SDK
+# Probe which field name the installed SDK exposes.
+_inputqp_has_steps = cc.compiles(
+  '''
+  #include <windows.h>
+  #include <mfapi.h>
+  void test() { InputQPSettings s; (void)s.steps; }
+  ''',
+  name : 'InputQPSettings::steps present',
+)
+if _inputqp_has_steps
+  message('InputQPSettings: using field "steps"')
+  mf_cpp_args += '-DINPUTQPSETTINGS_HAS_STEPS'
+else
+  _inputqp_has_step = cc.compiles(
+    '''
+    #include <windows.h>
+    #include <mfapi.h>
+    void test() { InputQPSettings s; (void)s.step; }
+    ''',
+    name : 'InputQPSettings::step present',
+  )
+  if _inputqp_has_step
+    message('InputQPSettings: using field "step"')
+  else
+    error('InputQPSettings has neither "steps" nor "step" — unsupported Windows SDK version')
+  endif
+endif
+
 mediafoundation_files = files(
   'codecapi.cpp',
   'encode.cpp',