use single quotes for grep command contained in double-quoted string

Author: bedroge

run_tests.sh

@@ -20,7 +20,7 @@ source ${base_dir}/init/eessi_defaults
 # Make sure we clone the latest version. This assumes versions are of the format "v1.2.3", then picks the latest
 # then checks it out
 TEST_CLONE="git clone https://github.com/EESSI/test-suite EESSI-test-suite && cd EESSI-test-suite"
-LATEST_VERSION="VERSION=\$(git tag | grep "^v[0-9]\+\.[0-9]\+\.[0-9]\+$" | sort -t. -k 1,1n -k 2,2n -k 3,3n | tail -1)"
+LATEST_VERSION="VERSION=\$(git tag | grep '^v[0-9]\+\.[0-9]\+\.[0-9]\+$' | sort -t. -k 1,1n -k 2,2n -k 3,3n | tail -1)"
 CHECKOUT_LATEST="git checkout \${VERSION}"
 
 # Git clone has to be run in compat layer, to make the git command available