Make sure we don't check for yasm version if we don't have yasm

configure.ac

@@ -1,4 +1,3 @@
-
 AC_INIT([cpuminer], [0.7.1])
 
 AC_PREREQ(2.52)
@@ -47,25 +46,24 @@ has_yasm=false
 AC_PATH_PROG(YASM,[yasm],[true yasm])
 if test "$YASM" = "false" ; then
   AC_MSG_WARN([yasm is required for the x86_64 SSE2 code, but it was not found])
-fi
-
-AC_MSG_CHECKING([if yasm version is greater than 1.0.1])
-yasmver=`yasm --version | head -1 | cut -d\  -f2`
-yamajor=`echo $yasmver | cut -d. -f1`
-yaminor=`echo $yasmver | cut -d. -f2`
-yamini=`echo $yasmver | cut -d. -f3`
-if test "$yamajor" -ge "1" ; then
-  if test "$yamajor" -eq "1" ; then
-    if test "$yaminor" -ge "0" ; then
-      if test "$yamini" -ge "1"; then
-        has_yasm=true
+else
+  AC_MSG_CHECKING([if yasm version is greater than 1.0.1])
+  yasmver=`yasm --version | head -1 | cut -d\  -f2`
+  yamajor=`echo $yasmver | cut -d. -f1`
+  yaminor=`echo $yasmver | cut -d. -f2`
+  yamini=`echo $yasmver | cut -d. -f3`
+  if test "$yamajor" -ge "1" ; then
+    if test "$yamajor" -eq "1" ; then
+      if test "$yaminor" -ge "0" ; then
+        if test "$yamini" -ge "1"; then
+          has_yasm=true
+        fi
       fi
     fi
+  else
+    has_yasm=false
   fi
-else
-has_yasm=false
 fi
-
 if test "x$has_yasm" != "x" ; then
   AC_MSG_RESULT([yes])
 else