Decouple install-ffmpeg on linux and macos specific files

The FFmpeg building flow has become too different on linux and macos.
Decoupling the logic makes it more simple to follow.

The CR also fixes nits and shellcheck warnings in install-ffmpeg.

Pick-to: 6.8 6.9
Change-Id: I28639d28c7210809e52ff18ce612da52f8754285
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>

coin/provisioning/common/macos/install-ffmpeg-macos.sh

@@ -0,0 +1,66 @@
+#!/usr/bin/env bash
+# Copyright (C) 2024 The Qt Company Ltd.
+# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+# This script builds and installs FFmpeg shared libs
+
+set -ex
+
+os="$1"
+
+if [ "$os" != "macos" ] && [ "$os" != "macos-universal" ]; then
+    >&2 echo "invalid os paremeter: $os"
+    exit 1
+fi
+
+source "${BASH_SOURCE%/*}/../unix/ffmpeg-installation-utils.sh"
+
+ffmpeg_source_dir=$(download_ffmpeg)
+ffmpeg_name=$(basename "$ffmpeg_source_dir")
+ffmpeg_config_options=$(get_ffmpeg_config_options "shared")
+prefix="/usr/local/$ffmpeg_name"
+
+build_ffmpeg() {
+    local arch="$1"
+    local build_dir="$ffmpeg_source_dir/build/$arch"
+    mkdir -p "$build_dir"
+    pushd "$build_dir"
+
+    # shellcheck disable=SC2086
+    if [ -n "$arch" ]; then
+        local cc="clang -arch $arch"
+        "$ffmpeg_source_dir/configure" $ffmpeg_config_options --prefix="$prefix" --enable-cross-compile --arch="$arch" --cc="$cc"
+    else
+        "$ffmpeg_source_dir/configure" $ffmpeg_config_options --prefix="$prefix"
+    fi
+    # shellcheck disable=
+
+    make install DESTDIR="$build_dir/installed" -j4
+    popd
+}
+
+brew install yasm
+export MACOSX_DEPLOYMENT_TARGET=12
+fix_relative_dependencies="${BASH_SOURCE%/*}/../macos/fix_relative_dependencies.sh"
+
+if [ "$os" == "macos"  ]; then
+    build_ffmpeg
+
+    install_dir="$ffmpeg_source_dir/build/installed"
+    "$fix_relative_dependencies" "$install_dir/usr/local/$ffmpeg_name/lib"
+    sudo mv "$install_dir/usr/local/$ffmpeg_name" "/usr/local"
+else
+    build_ffmpeg "arm64"
+    build_ffmpeg "x86_64"
+
+    arm64_install_dir="$ffmpeg_source_dir/build/arm64/installed"
+    x86_64_install_dir="$ffmpeg_source_dir/build/x86_64/installed"
+
+    "$fix_relative_dependencies" "$arm64_install_dir/usr/local/$ffmpeg_name/lib"
+    "$fix_relative_dependencies" "$x86_64_install_dir/usr/local/$ffmpeg_name/lib"
+
+    sudo rm -rf "/usr/local/$ffmpeg_name" # lipo fails upon 2nd run
+    sudo "${BASH_SOURCE%/*}/../macos/makeuniversal.sh" "$arm64_install_dir" "$x86_64_install_dir"
+fi
+
+set_ffmpeg_dir_env_var "FFMPEG_DIR" "/usr/local/$ffmpeg_name"