fix compiler detection in makefile

Reducibility_Multiplex/Makefile

@@ -1,12 +1,33 @@
 CC=gcc
-CFLAGS=-Iinclude -g -O3 
+CFLAGS=-O2 
+LDFLAGS=-lm -lgmp -lz
 
 
-all: reducibility
+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), 0)
+# compiler is GCC
+		CFLAGS+=-fopenmp
+else
+ifneq ($(IS_CC_CLANG), 0)
+# compiler is CLANG
+		LDFLAGS+=-lomp
+else 
+ifneq($(IS_CC_ICC), 0)
+# compiler is Intel icc
+			CFLAGS+=-qopenmp
+endif
+endif
+
+
+all: reducibility_complexity
 
 clean:
 	rm -f reducibility_complexity
 
 reducibility: reducibility_complexity.c
-	$(CC) $(CFLAGS) reducibility_complexity.c  -fopenmp -lm -lgmp -lz -o  reducibility_complexity
+	$(CC) $(CFLAGS) $(LDFLAGS)  reducibility_complexity.c  -o  reducibility_complexity