fix condition typo

Author: facchinm

package-avr-gcc.bash

@@ -81,7 +81,7 @@ rm -rf objdir/{info,man,share}
 
 # if producing a windows build, compress as zip and
 # copy *toolchain-precompiled* content to any folder containing a .exe
-[ if ${OUTPUT_TAG} == *"mingw"* ]; then
+if [[ ${OUTPUT_TAG} == *"mingw"* ]] ; then
 
   rm -f avr-gcc-${OUTPUT_VERSION}-${OUTPUT_TAG}.zip
   mv objdir avr