Correctly detect FreeBSD when configuring.

Thanks to yurivict for helping.
Closes qbittorrent#2962.

Author: sledgehammer999

configure

@@ -4263,7 +4263,7 @@ fi
 # Detect OS
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether OS is FreeBSD" >&5
 $as_echo_n "checking whether OS is FreeBSD... " >&6; }
-if test "x$host_os" = "x*FreeBSD*"; then :
+if expr "$host_os" : ".*freebsd.*" > /dev/null; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }
       LIBS="-lexecinfo $LIBS"

configure.ac

@@ -74,7 +74,7 @@ AC_ARG_ENABLE(qt-dbus,
 
 # Detect OS
 AC_MSG_CHECKING([whether OS is FreeBSD])
-AS_IF([test "x$host_os" = "x*FreeBSD*"],
+AS_IF([expr "$host_os" : ".*freebsd.*" > /dev/null],
       [AC_MSG_RESULT([yes])
       LIBS="-lexecinfo $LIBS"],
       [AC_MSG_RESULT([no])])