configure: remove bogus uname platform checks

calling uname in a configure script is entirely bogus, as it will return
wrong results in crosscompilation scenarios. the only sensible way to
detect the target platform's peculiarities is to test the preprocessor
for macros defining the target.

configure

@@ -14,22 +14,6 @@ done
 set +C
 trap 'rm "$tmpc"' EXIT INT QUIT TERM HUP
 
-ismac() {
-	uname -s | grep Darwin >/dev/null
-}
-
-isx86_64() {
-	uname -m | grep -i X86_64 >/dev/null
-}
-
-isbsd() {
-	uname -s | grep BSD >/dev/null
-}
-
-isopenbsd() {
-	uname -s | grep OpenBSD >/dev/null
-}
-
 check_compile() {
 	printf "checking %s ... " "$1"
 	printf "$3" > "$tmpc"
@@ -73,7 +57,7 @@ usage() {
 	echo "--ignore-cve              default: no"
 	echo "	if set to yes ignores CVE-2015-3887 and makes it possible"
 	echo "	to preload from current dir (insecure)"
-	ismac && isx86_64 && echo "--fat-binary : build for both i386 and x86_64 architectures on 64-bit Macs"
+	echo "--fat-binary : build for both i386 and x86_64 architectures on 64-bit Macs"
 	echo "--help : show this text"
 	exit 1
 }
@@ -133,10 +117,33 @@ if [ -z "$CC" ] ; then
 	CC=cc
 fi
 
-check_define __OpenBSD__ && \
+
+bsd_detected=false
+isbsd() {
+	$bsd_detected
+}
+mac_detected=false
+ismac() {
+	$mac_detected
+}
+mac_64=false
+ismac64() {
+	$mac_64
+}
+
+
+check_define __APPLE__ && {
+	mac_detected=true
+	check_define __x86_64__ && mac_64=true
+}
+check_define __FreeBSD__ && bsd_detected=true
+check_define __OpenBSD__ && {
+bsd_detected=true
+echo "CFLAGS+=-DIS_OPENBSD">>config.mak
 check_compile_run 'whether OpenBSDs fclose() (illegally) calls close()' \
 '#include <stdio.h>\n#include<stdlib.h>\nint close(int x){exit(0);}int main(){fclose(stdin);return 1;}' && \
 OUR_CPPFLAGS="$OUR_CPPFLAGS -DBROKEN_FCLOSE"
+}
 
 echo "CC=$CC">config.mak
 [ -z "$CPPFLAGS" ] || echo "CPPFLAGS=$CPPFLAGS">>config.mak
@@ -155,7 +162,7 @@ if ismac ; then
 	echo NO_AS_NEEDED=>>config.mak
 	echo LDSO_SUFFIX=dylib>>config.mak
 	echo MAC_CFLAGS+=-DIS_MAC=1>>config.mak
-	if isx86_64 && [ "$fat_binary" = 1 ] ; then
+	if ismac64 && [ "$fat_binary" = 1 ] ; then
 		echo "Configuring a fat binary for i386 and x86_64"
 		echo MAC_CFLAGS+=-arch i386 -arch x86_64>>config.mak
 		echo LDFLAGS+=-arch i386 -arch x86_64>>config.mak
@@ -164,7 +171,6 @@ if ismac ; then
 elif isbsd ; then
 	echo LIBDL=>>config.mak
 	echo "CFLAGS+=-DIS_BSD">>config.mak
-	isopenbsd && echo "CFLAGS+=-DIS_OPENBSD">>config.mak
 	make_cmd=gmake
 fi