scripts: fix shell scripts according to shellcheck errors

Unify coding style of shell scripts in accordance with
shellcheck errors.

Signed-off-by: Ruslan Mstoi <ruslan.mstoi@intel.com>

scripts/run_integration_tests_vfio.sh

@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+# shellcheck disable=SC2048,SC2086
 set -x
 
 # This set of vfio tests require to be ran on a specific machine with
@@ -7,8 +8,9 @@ set -x
 # out of the scope of this script, including the custom guest image with
 # Nvidia drivers installed, and properly configured Nvidia Tesla T4 card.
 
-source $HOME/.cargo/env
-source $(dirname "$0")/test-util.sh
+# shellcheck source=/dev/null
+source "$HOME"/.cargo/env
+source "$(dirname "$0")"/test-util.sh
 
 process_common_args "$@"
 
@@ -18,10 +20,11 @@ download_hypervisor_fw
 
 CFLAGS=""
 if [[ "${BUILD_TARGET}" == "x86_64-unknown-linux-musl" ]]; then
+    # shellcheck disable=SC2034
     CFLAGS="-I /usr/include/x86_64-linux-musl/ -idirafter /usr/include/"
 fi
 
-cargo build --features mshv --all --release --target $BUILD_TARGET
+cargo build --features mshv --all --release --target "$BUILD_TARGET"
 
 export RUST_BACKTRACE=1
 time cargo test "vfio::test_nvidia" -- --test-threads=1 ${test_binary_args[*]}