--- ./configure.ac	2020-03-29 20:55:44.217480719 -0700
+++ ./configure.ac	2020-03-29 20:57:12.190473099 -0700
@@ -169,45 +169,45 @@
 	else
 		CFLAGS=""
 		dnl O3 generally gives better performance than O2 in both Intel and ARM
-		AC_CHECK_CC_OPT([-O3], [CFLAGS="$CFLAGS -O3"], [])
+		AX_CHECK_COMPILE_FLAG([-O3], [CFLAGS="$CFLAGS -O3"], [])
 
 		if test $ac_enable_32 = yes ; then
 			dnl Force build for 32 bit x86
-			AC_CHECK_CC_OPT([-m32 -march=i686], [CFLAGS="$CFLAGS -m32 -march=i686"], [])
-			AC_CHECK_CC_OPT([-fomit-frame-pointer], [CFLAGS="$CFLAGS -fomit-frame-pointer"], [])
+			AX_CHECK_COMPILE_FLAG([-m32 -march=i686], [CFLAGS="$CFLAGS -m32 -march=i686"], [])
+			AX_CHECK_COMPILE_FLAG([-fomit-frame-pointer], [CFLAGS="$CFLAGS -fomit-frame-pointer"], [])
 		elif $GREP a02082\\\|a22082 /proc/cpuinfo >/dev/null 2>&1; then
 			dnl Raspberry Pi 3
 			dnl GCC 4 has problems with -march=native in Raspbian,
 			dnl resulting in a "double free or corruption" error
 			dnl See: https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=139091
-			AC_CHECK_CC_OPT([-march=armv8-a+crc], [CFLAGS="$CFLAGS -march=armv8-a+crc"], [])
-			AC_CHECK_CC_OPT([-mtune=cortex-a53], [CFLAGS="$CFLAGS -mtune=cortex-a53"], [])
-			AC_CHECK_CC_OPT([-mfloat-abi=hard], [CFLAGS="$CFLAGS -mfloat-abi=hard"], [])
-			AC_CHECK_CC_OPT([-mfpu=crypto-neon-fp-armv8], [CFLAGS="$CFLAGS -mfpu=crypto-neon-fp-armv8"], [])
-			AC_CHECK_CC_OPT([-funsafe-math-optimizations], [CFLAGS="$CFLAGS -funsafe-math-optimizations"], [])
+			AX_CHECK_COMPILE_FLAG([-march=armv8-a+crc], [CFLAGS="$CFLAGS -march=armv8-a+crc"], [])
+			AX_CHECK_COMPILE_FLAG([-mtune=cortex-a53], [CFLAGS="$CFLAGS -mtune=cortex-a53"], [])
+			AX_CHECK_COMPILE_FLAG([-mfloat-abi=hard], [CFLAGS="$CFLAGS -mfloat-abi=hard"], [])
+			AX_CHECK_COMPILE_FLAG([-mfpu=crypto-neon-fp-armv8], [CFLAGS="$CFLAGS -mfpu=crypto-neon-fp-armv8"], [])
+			AX_CHECK_COMPILE_FLAG([-funsafe-math-optimizations], [CFLAGS="$CFLAGS -funsafe-math-optimizations"], [])
 			dnl Raspberry Pi 2
 		elif $GREP a01040\\\|a01041\\\|a21041\\\|a22042 /proc/cpuinfo >/dev/null 2>&1; then
-			AC_CHECK_CC_OPT([-march=armv7-a], [CFLAGS="$CFLAGS -march=armv7-a"], [])
-			AC_CHECK_CC_OPT([-mfpu=neon-vfpv4], [CFLAGS="$CFLAGS -mfpu=neon-vfpv4"], [])
+			AX_CHECK_COMPILE_FLAG([-march=armv7-a], [CFLAGS="$CFLAGS -march=armv7-a"], [])
+			AX_CHECK_COMPILE_FLAG([-mfpu=neon-vfpv4], [CFLAGS="$CFLAGS -mfpu=neon-vfpv4"], [])
 		else
-			AC_CHECK_CC_OPT([-march=native], [CFLAGS="$CFLAGS -march=native"], [])
-			AC_CHECK_CC_OPT([-fomit-frame-pointer], [CFLAGS="$CFLAGS -fomit-frame-pointer"], [])
+			AX_CHECK_COMPILE_FLAG([-march=native], [CFLAGS="$CFLAGS -march=native"], [])
+			AX_CHECK_COMPILE_FLAG([-fomit-frame-pointer], [CFLAGS="$CFLAGS -fomit-frame-pointer"], [])
 		fi
 
 		dnl Code was written when compilers where not aggressively optimizing undefined behaviour about aliasing
 		dnl WARNING! At present disabled to maximize performance
-		dnl AC_CHECK_CC_OPT([-fno-strict-aliasing], [CFLAGS="$CFLAGS -fno-strict-aliasing"], [])
+		dnl AX_CHECK_COMPILE_FLAG([-fno-strict-aliasing], [CFLAGS="$CFLAGS -fno-strict-aliasing"], [])
 		dnl Code was written when compilers where not aggressively optimizing undefined behaviour about overflow in signed integers
 		dnl WARNING! At present disabled to maximize performance
-		dnl AC_CHECK_CC_OPT([-fno-strict-overflow], [CFLAGS="$CFLAGS -fno-strict-overflow"], [])
+		dnl AX_CHECK_COMPILE_FLAG([-fno-strict-overflow], [CFLAGS="$CFLAGS -fno-strict-overflow"], [])
 		dnl Code was written on Intel where char is signed
-		AC_CHECK_CC_OPT([-fsigned-char], [CFLAGS="$CFLAGS -fsigned-char"], [])
+		AX_CHECK_COMPILE_FLAG([-fsigned-char], [CFLAGS="$CFLAGS -fsigned-char"], [])
 		dnl We are not interested in stack protection
-		AC_CHECK_CC_OPT([-fno-stack-protector], [CFLAGS="$CFLAGS -fno-stack-protector"], [])
+		AX_CHECK_COMPILE_FLAG([-fno-stack-protector], [CFLAGS="$CFLAGS -fno-stack-protector"], [])
 		dnl Some useful warnings
-		AC_CHECK_CC_OPT([-Wall], [CFLAGS="$CFLAGS -Wall"], [])
-		AC_CHECK_CC_OPT([-Wno-sign-compare], [CFLAGS="$CFLAGS -Wno-sign-compare"], [])
-		AC_CHECK_CC_OPT([-Wno-unused], [CFLAGS="$CFLAGS -Wno-unused"], [])
+		AX_CHECK_COMPILE_FLAG([-Wall], [CFLAGS="$CFLAGS -Wall"], [])
+		AX_CHECK_COMPILE_FLAG([-Wno-sign-compare], [CFLAGS="$CFLAGS -Wno-sign-compare"], [])
+		AX_CHECK_COMPILE_FLAG([-Wno-unused], [CFLAGS="$CFLAGS -Wno-unused"], [])
 	fi
 	if test ! -z $ac_host_cflags; then
 		CFLAGS="$ac_host_cflags $CFLAGS"