Support eval bash statement in ./compile.sh (#1616)

Currently, invoking compile.sh will run its mono task of building all the
components into a final image.

In some situation, especially when developing with Kernel or U-Boot, it is
handy to run a portion of that great task like:

    export BOARD=firefly-rk3399
    export BRANCH=dev
    # more to avoid the popup of dialog
    ./compile.sh 'fetch_from_repo "$BOOTSOURCE" "$BOOTDIR" "$BOOTBRANCH" "yes"'
    ./compile.sh 'compile_uboot'

or use a profile to keep things simple:

    ./compile.sh default BRANCH=dev 'compile_uboot'

compile.sh

@@ -169,6 +169,7 @@ fi
 
 if [[ -z "$CONFIG" && -n "$1" && -f "${SRC}/userpatches/config-$1.conf" ]]; then
 	CONFIG="userpatches/config-$1.conf"
+	shift
 fi
 
 # usind default if custom not found
@@ -195,13 +196,12 @@ popd > /dev/null
 [[ -z "${USERPATCHES_PATH}" ]] && USERPATCHES_PATH="$CONFIG_PATH"
 
 # Script parameters handling
-for i in "$@"; do
-	if [[ $i == *=* ]]; then
-		parameter=${i%%=*}
-		value=${i##*=}
-		display_alert "Command line: setting $parameter to" "${value:-(empty)}" "info"
-		eval "$parameter=\"$value\""
-	fi
+while [[ $1 == *=* ]]; do
+    parameter=${1%%=*}
+    value=${1##*=}
+    shift
+    display_alert "Command line: setting $parameter to" "${value:-(empty)}" "info"
+    eval "$parameter=\"$value\""
 done
 
 if [[ $BUILD_ALL == yes || $BUILD_ALL == demo ]]; then