twister: error if valgrind executable not found

if --enable-valgrind is selected but no valgrind executable can be
found in PATH, exit with an error

Signed-off-by: Mikkel Jakobsen <mikkel.aunsbjerg@escolifesciences.com>

scripts/pylib/twister/twisterlib.py

@@ -578,7 +578,7 @@ class BinaryHandler(Handler):
             command = [self.binary]
 
         run_valgrind = False
-        if self.valgrind and shutil.which("valgrind"):
+        if self.valgrind:
             command = ["valgrind", "--error-exitcode=2",
                        "--leak-check=full",
                        "--suppressions=" + ZEPHYR_BASE + "/scripts/valgrind.supp",

scripts/twister

@@ -882,6 +882,10 @@ def main():
         logger.error("west-flash requires device-testing to be enabled")
         sys.exit(1)
 
+    if options.enable_valgrind and not shutil.which("valgrind"):
+        logger.error("valgrind enabled but valgrind executable not found")
+        sys.exit(1)
+
     if options.coverage:
         options.enable_coverage = True