trailingWhitespace test now provides the line number when test fails

Author: Cyan4973

Makefile

@@ -528,7 +528,7 @@ listL120:  # extract lines >= 120 characters in *.{c,h}, by Takayuki Matsuoka (n
 
 .PHONY: trailingWhitespace
 trailingWhitespace:
-	! $(GREP) -E "`printf '[ \\t]$$'`" cli/*.c cli/*.h cli/*.1 *.c *.h LICENSE Makefile build/cmake/CMakeLists.txt
+	@$(GREP) -n -E "`printf '[ \\t]$$'`" cli/*.c cli/*.h cli/*.1 *.c *.h LICENSE Makefile build/cmake/CMakeLists.txt && { echo "Error: trailing whitespace detected"; exit 1; } || true
 
 .PHONY: lint-unicode
 lint-unicode: