Use dirname $0 in localization scripts

Languages/update-source-strings.sh

@@ -3,7 +3,7 @@
 # This script updates the dolphin-emu.pot file to match the strings in
 # the source code.
 
-cd ${0/update-source-strings.sh/}/..
+cd "$(dirname "$0")/.."
 SRCDIR=Source
 find $SRCDIR -name '*.cpp' -o -name '*.h' -o -name '*.c' | \
 	xgettext -d dolphin-emu -s --keyword=_ --keyword=wxTRANSLATE --keyword=SuccessAlertT \

Languages/update-translated-strings.sh

@@ -5,6 +5,6 @@
 # script before committing changes to the .po files, otherwise the .po
 # files might get modified the next time you try to build using cmake.
 
-cd ${0/update-translated-strings.sh/}/..
+cd "$(dirname "$0")/.."
 POTFILE=./Languages/po/dolphin-emu.pot
 find ./Languages/po -name '*.po' -exec msgmerge --quiet --update --backup=none -s {} $POTFILE \;