Add Makefile command to run checkbashisms on all /bin/sh scripts

Based on the shellcheck make target, add a target which checks
for violations of POSIX standards for shell scripts

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Gabriel A. Devenyi <gdevenyi@gmail.com>
Closes #10513

Makefile.am

@@ -114,7 +114,7 @@ endif
 endif
 
 PHONY += codecheck
-codecheck: cstyle shellcheck flake8 mancheck testscheck vcscheck
+codecheck: cstyle shellcheck checkbashisms flake8 mancheck testscheck vcscheck
 
 PHONY += checkstyle
 checkstyle: codecheck commitcheck
@@ -146,6 +146,22 @@ shellcheck:
 		echo "skipping shellcheck because shellcheck is not installed"; \
 	fi
 
+PHONY += checkbashisms
+checkbashisms:
+	@if type checkbashisms > /dev/null 2>&1; then \
+		checkbashisms -n -p -x \
+			$$(find ${top_srcdir} \
+				-name '.git' -prune \
+				-o -name 'build' -prune \
+				-o -name 'tests' -prune \
+				-o -name 'config' -prune \
+				-o -type f ! -name 'config*' \
+				! -name 'libtool' \
+			-exec bash -c 'awk "NR==1 && /\#\!.*bin\/sh.*/ {print FILENAME;}" "{}"' \;); \
+	else \
+		echo "skipping checkbashisms because checkbashisms is not installed"; \
+	fi
+
 PHONY += mancheck
 mancheck:
 	@if type mandoc > /dev/null 2>&1; then \