Cmake out of tree build fixes.

nheko.spec

@@ -1,3 +1,4 @@
+%undefine __cmake_in_source_build
 %bcond_without clang
 
 %if %{with clang}
@@ -63,11 +64,9 @@ for Matrix that feels more like a mainstream chat app.
 
 %prep
 %autosetup -p1
-mkdir -p %{_target_platform}
 
 %build
-pushd %{_target_platform}
-    %cmake -G Ninja \
+%cmake -G Ninja \
 %if %{with clang}
     -DCMAKE_C_COMPILER=%{_bindir}/clang \
     -DCMAKE_CXX_COMPILER=%{_bindir}/clang++ \
@@ -94,13 +93,11 @@ pushd %{_target_platform}
     -DUSE_BUNDLED_TWEENY:BOOL=OFF \
     -DUSE_BUNDLED_JSON:BOOL=OFF \
     -DUSE_BUNDLED_OPENSSL:BOOL=OFF \
-    -DUSE_BUNDLED_SODIUM:BOOL=OFF \
-    ..
-popd
-%ninja_build -C %{_target_platform}
+    -DUSE_BUNDLED_SODIUM:BOOL=OFF
+%cmake_build
 
 %install
-%ninja_install -C %{_target_platform}
+%cmake_install
 
 %check
 appstream-util validate-relax --nonet %{buildroot}%{_metainfodir}/%{name}.appdata.xml