function symlink_contents_to_dir() {
if [[ -z "$1" ]]; then
echo "arg 1 to symlink_contents_to_dir is unexpectedly empty"
exit 1
fi
if [[ -z "$2" ]]; then
echo "arg 2 to symlink_contents_to_dir is unexpectedly empty"
exit 1
fi
local target="$2"
mkdir -p "$target"
local replace_in_files="${3:-}"
if [[ -f "$1" ]]; then
symlink_to_dir "$1" "$target" "$replace_in_files"
elif [[ -L "$1" && ! -d "$1" ]]; then
local actual=$(readlink "$1")
symlink_contents_to_dir "$actual" "$target" "$replace_in_files"
elif [[ -d "$1" ]]; then
SAVEIFS=$IFS
IFS=$'
'
local children=($(find "$1/" -maxdepth 1 -mindepth 1))
IFS=$SAVEIFS
for child in "${children[@]:-}"; do
symlink_to_dir "$child" "$target" "$replace_in_files"
done
fi
}
function symlink_to_dir() {
if [[ -z "$1" ]]; then
echo "arg 1 to symlink_to_dir is unexpectedly empty"
exit 1
fi
if [[ -z "$2" ]]; then
echo "arg 2 to symlink_to_dir is unexpectedly empty"
exit 1
fi
local target="$2"
mkdir -p "$target"
local replace_in_files="${3:-}"
if [[ -f "$1" ]]; then
# In order to be able to use `replace_in_files`, we ensure that we create copies of specfieid
# files so updating them is possible.
if [[ "$1" == *.pc || "$1" == *.la || "$1" == *-config || "$1" == *.mk || "$1" == *.cmake ]]; then
dest="$target/$(basename "$1")"
cp "$1" "$dest" && chmod +w "$dest" && touch -r "$1" "$dest"
else
ln -s -f "$1" "$target"
fi
elif [[ -L "$1" && ! -d "$1" ]]; then
cp -pR "$1" "$2"
elif [[ -d "$1" ]]; then

# If not replacing in files, simply create a symbolic link rather than traversing tree of files, which can result in very slow builds
if [[ "$replace_in_files" = False ]]; then
ln -s -f "$1" "$target"
return
fi

SAVEIFS=$IFS
IFS=$'
'
local children=($(find "$1/" -maxdepth 1 -mindepth 1))
IFS=$SAVEIFS
local dirname=$(basename "$1")
mkdir -p "$target/$dirname"
for child in "${children[@]:-}"; do
if [[ -n "$child" && "$dirname" != *.ext_build_deps ]]; then
symlink_to_dir "$child" "$target/$dirname" "$replace_in_files"
fi
done
else
echo "Can not copy $1"
fi
}
symlink_contents_to_dir $SOURCE_DIR $TARGET_DIR False