add user-flags
add ffnvcodec if required, because autodetect is disabled
disable lto, handled by user-flags
--- a/avidemux_core/cmake/ffmpeg_configure.sh.cmake
+++ b/avidemux_core/cmake/ffmpeg_configure.sh.cmake
@@ -1,2 +1,2 @@
 export PATH=${FF_ENV_PATH}:$PATH
-${FFMPEG_SOURCE_DIR}/configure ${FFMPEG_FLAGS}
\ No newline at end of file
+${FFMPEG_SOURCE_DIR}/configure ${FFMPEG_FLAGS} @@GENTOO_FFMPEG_FLAGS@@
\ No newline at end of file
--- a/avidemux_core/cmake/admFFmpegBuild_native.cmake
+++ b/avidemux_core/cmake/admFFmpegBuild_native.cmake
@@ -8,6 +8,7 @@ ADM_FF_SET_DEFAULT()
 IF(USE_NVENC)
   SET(FFMPEG_ENCODERS ${FFMPEG_ENCODERS} nvenc)
   SET(FFMPEG_DECODERS ${FFMPEG_DECODERS} nvdec)
+  xadd("--enable-ffnvcodec")
   xadd("--enable-nvenc")
   xadd("--enable-nvdec")
   xadd("--extra-cflags=-I${NVENC_INCLUDE_DIR}")
@@ -44,10 +45,6 @@ IF(APPLE AND "$ENV{MACOSX_DEPLOYMENT_TARGET}" VERSION_EQUAL "10.15")
   xadd(--extra-cflags="-fno-stack-check") # see https://trac.ffmpeg.org/ticket/8073
 ENDIF()
 
-IF(NOT APPLE AND NOT ADM_CPU_X86_32 AND NOT "${CMAKE_C_COMPILER}" MATCHES ".*[cC]lang.*")
-  xadd(--enable-lto)
-ENDIF()
-
 #@@
 ADM_FF_ADD_OPTIONS()