fixed other error in compiler check

Reducibility_Multiplex/Makefile

@@ -2,26 +2,24 @@ CC=gcc
 CFLAGS=-O2 
 LDFLAGS=-lm -lgmp -lz
 
-HAVE_CC=$(shell $(CC) --version ; echo \$?)
 
-IS_CC_GCC=$(shell $(CC) --version | grep -Eic 'gcc' || echo "NUL")
-IS_CC_CLANG=$(shell $(CC) --version | grep -Eic '(llvm|clang)' || echo "NUL") 
-IS_CC_ICC=$(shell $(CC) --version | grep -Eic 'Intel' || echo "NUL")
+IS_CC_GCC=$(shell $(CC) --version 2>/dev/null | grep -Eic 'gcc')
+IS_CC_CLANG=$(shell $(CC) --version | grep -Eic '(llvm|clang)') 
+IS_CC_ICC=$(shell $(CC) --version | grep -Eic 'Intel')
 
 
-ifneq ($(IS_CC_GCC),"NUL")
+ifneq ($(IS_CC_GCC), 0)
 # compiler is GCC
-	CFLAGS+=-fopenmp
+		CFLAGS+=-fopenmp
 else
-    ifneq ($(IS_CC_CGLANG), "NUL")
+ifneq ($(IS_CC_CLANG), 0)
 # compiler is CLANG
-	LDFLAGS+=-lomp
-    else 
-         ifneq ($(IS_CC_ICC), "NUL")
+		LDFLAGS+=-lomp
+else 
+ifneq($(IS_CC_ICC), 0)
 # compiler is Intel icc
-		CFLAGS+=-qopenmp
-         endif
-    endif
+			CFLAGS+=-qopenmp
+endif
 endif