From 2b1f0e0db1196390852c1cec5917a0ce7f4d24df Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 23 Sep 2016 10:12:22 -0400
Subject: [PATCH] Don't shell out to kpsewhich for undefined variables.

---
 makefile | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/makefile b/makefile
index d9bd9d5..a0b130e 100644
--- a/makefile
+++ b/makefile
@@ -25,7 +25,13 @@ MJOTEX += mjo-theorem-star.tex mjo-topology.tex
 # Use kpsewhich (from the kpathsea suite) to find the absolute paths
 # of the bibtex/mjotex files listed in in $(BIBS)/$(MJOTEX). The SRCS
 # variable should contain all (Bib)TeX source files for the document.
-SRCS = $(PN).tex $(shell kpsewhich $(BIBS)) $(shell kpsewhich $(MJOTEX))
+SRCS = $(PN).tex
+ifdef BIBS
+SRCS += $(shell kpsewhich $(BIBS))
+endif
+ifdef MJOTEX
+SRCS += $(shell kpsewhich $(MJOTEX))
+endif
 
 
 # The first target is the default, so put the PDF document first.
-- 
2.43.2