diff -ru gmic-1.6.8.orig3/src/Makefile gmic-1.6.8/src/Makefile
--- gmic-1.6.8.orig3/src/Makefile	2015-12-21 12:24:21.000000000 +0100
+++ gmic-1.6.8/src/Makefile	2015-12-21 12:30:42.152075848 +0100
@@ -145,9 +145,11 @@
 # (may slow down the code a little bit).
 CIMG_ABORT_CFLAGS = -Dcimg_use_abort
 
+ifndef NO_OPENMP
 # Flags to enable parallelization using OpenMP.
 OPENMP_CFLAGS = -fopenmp -Dcimg_use_openmp
 OPENMP_LIBS = -lgomp
+endif
 
 # Flags to enable image display, using X11
 # (keep /usr/ dirname here since X11 is located in /usr/ on Mac too).