Fix some issues in shell scripts spotted by shellcheck

.travis/script.sh

@@ -22,7 +22,7 @@ else
 	"$TRAVIS_BUILD_DIR/.travis/$TRAVIS_OS_NAME.$TARGET_OS.script.sh"
 
 	# Package and upload non-tagged builds
-	if [ ! -z "$TRAVIS_TAG" ]; then
+	if [ -n "$TRAVIS_TAG" ]; then
 		# Skip, handled by travis deploy instead
 		exit 0
 	elif [[ $TARGET_OS == win* ]]; then

cmake/linux/package_linux.sh.in

@@ -108,7 +108,7 @@ chmod +x "${APPDIR}usr/bin/lmms"
 unset LD_LIBRARY_PATH
 
 # Ensure linuxdeployqt can find shared objects
-export LD_LIBRARY_PATH="${APPDIR}usr/lib/lmms/":"${APPDIR}usr/lib/lmms/optional":$LD_LIBRARY_PATH
+export LD_LIBRARY_PATH="${APPDIR}"usr/lib/lmms/:"${APPDIR}"usr/lib/lmms/optional:"$LD_LIBRARY_PATH"
 
 # Handle wine linking
 if [ -d "@WINE_32_LIBRARY_DIR@" ]; then

cmake/msys/extract_debs.sh

@@ -1,4 +1,6 @@
 #!/bin/bash
+set -e
+
 ppa_dir=./ppa/
 
 pushd $ppa_dir

cmake/msys/msys_helper.sh

@@ -68,7 +68,7 @@ stkver="4.5.1"
 mingw_root="/$(echo "$MSYSTEM"|tr '[:upper:]' '[:lower:]')"
 
 info "Downloading and building fltk $fltkver"
-if ! which fluid; then
+if ! command -v fluid; then
 	wget http://fltk.org/pub/fltk/$fltkver/fltk-$fltkver-source.tar.gz -O "$HOME/fltk-source.tar.gz"
 	tar zxf "$HOME/fltk-source.tar.gz" -C "$HOME/"
 	pushd "$HOME/fltk-$fltkver"