fix(scripts): address shellcheck errs

Signed-off-by: Vaughn Dice <vaughn.dice@fermyon.com>

scripts/bump-spin-formula.sh

@@ -16,7 +16,7 @@ usage() {
     echo "Example: $0 v3.0.0"
 }
 
-if [ $# -ne 1 ]; then
+if [[ $# -ne 1 ]]; then
     usage
     exit 1
 fi
@@ -28,20 +28,20 @@ if [[ ! "${VERSION}" =~ ^v[0-9]+.[0-9]+.[0-9]+$ ]]; then
 fi
 
 # Get the checksum file for the release
-wget -qO checksums.txt "https://github.com/fermyon/spin/releases/download/$VERSION/checksums-$VERSION.txt" || \
-    (echo "Checksum file not found for version $VERSION" && exit 1)
+wget -qO checksums.txt "https://github.com/fermyon/spin/releases/download/${VERSION}/checksums-${VERSION}.txt" || \
+    (echo "Checksum file not found for version ${VERSION}" && exit 1)
 
 # Remove the 'v' prefix from the version
 ERSION="${VERSION:1}"
-$SED_INPLACE -e "s/version \"[^\"]*\"/version \"$ERSION\"/" $FORMULA
+${SED_INPLACE} -e "s/version \"[^\"]*\"/version \"${ERSION}\"/" "${FORMULA}"
 # Update the sha256 checksums for each OS/Arch
 while read -r line; do
-    filename=$(echo "$line" | awk '{print $2}')
-    sha256=$(echo "$line" | awk '{print $1}')
-    os_arch=$(echo ${filename} | sed "s/spin-v${ERSION}-//g")
-    if grep -q "$os_arch" $FORMULA; then
-        $SED_INPLACE -E "/url \".*$os_arch\"/ { n; s/sha256 \"[^\"]*\"/sha256 \"$sha256\"/; }" $FORMULA
+    filename=$(echo "${line}" | awk '{print $2}')
+    sha256=$(echo "${line}" | awk '{print $1}')
+    os_arch="${filename//spin-v${ERSION}-/}"
+    if grep -q "${os_arch}" "${FORMULA}"; then
+        ${SED_INPLACE} -E "/url \".*${os_arch}\"/ { n; s/sha256 \"[^\"]*\"/sha256 \"${sha256}\"/; }" "${FORMULA}"
     fi
 done < checksums.txt
 
-echo "Formula updated to version $VERSION with new checksums."
+echo "Formula updated to version ${VERSION} with new checksums."