Use kcov from official Ubuntu 20.04 repository (#25385)

* Ubuntu 20.04 provides kcov, so don't build from source

* Use two undocumented options for kcov v3.8

share/spack/qa/bashcov

@@ -9,4 +9,7 @@ if [ -z "$SPACK_ROOT" ]; then
     exit 1
 fi
 
-kcov "$SPACK_ROOT/coverage" "$@"
+# Using a -- to separate the script to be tested from kcov is not documented
+# as of v38, but seems to work. The same is true for the "--debug-force-bash-stderr"
+# option, see https://github.com/SimonKagstrom/kcov/issues/61
+kcov --debug-force-bash-stderr "$SPACK_ROOT/coverage" -- "$@"

share/spack/qa/run-shell-tests

@@ -38,8 +38,8 @@ cd "$SPACK_ROOT"
 # Run bash tests with coverage enabled, but pipe output to /dev/null
 # because it seems that kcov seems to undo the script's redirection
 if [ "$COVERAGE" = true ]; then
-    "$QA_DIR/bashcov" "$QA_DIR/setup-env-test.sh" &> /dev/null
-    "$QA_DIR/bashcov" "$QA_DIR/completion-test.sh" &> /dev/null
+    kcov "$SPACK_ROOT/coverage" "$QA_DIR/setup-env-test.sh" &> /dev/null
+    kcov "$SPACK_ROOT/coverage" "$QA_DIR/completion-test.sh" &> /dev/null
 else
     bash "$QA_DIR/setup-env-test.sh"
     bash "$QA_DIR/completion-test.sh"

share/spack/qa/setup.sh

@@ -31,10 +31,10 @@ if [[ "$COVERAGE" == "true" ]]; then
     bashcov=$(realpath ${QA_DIR}/bashcov)
 
     # instrument scripts requiring shell coverage
-    sed -i~ "s@#\!/bin/bash@#\!${bashcov}@" "$SPACK_ROOT/lib/spack/env/cc"
+    sed -i "s@#\!/bin/bash@#\!${bashcov}@" "$SPACK_ROOT/lib/spack/env/cc"
     if [ "$(uname -o)" != "Darwin" ]; then
         # On darwin, #! interpreters must be binaries, so no sbang for bashcov
-        sed -i~ "s@#\!/bin/sh@#\!${bashcov}@"   "$SPACK_ROOT/bin/sbang"
+        sed -i "s@#\!/bin/sh@#\!${bashcov}@"   "$SPACK_ROOT/bin/sbang"
     fi
 fi