configure: Enable dead code (lzo, snappy, quorum)

Those options were not enabled by default, even when the build
environment would have supported them, so the corresponding
code was not compiled in normal test builds like on build bots.

[Building quorum by default "broke" qemu-iotests ./check 081.  It turns
out the 081.out master output was just bitrotted.  Fix this by updating
the error message.
--Stefan]

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Qiao Nuohan <qiaonuohan@cn.fujitsu.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

configure

@@ -311,8 +311,8 @@ libusb=""
 usb_redir=""
 glx=""
 zlib="yes"
-lzo="no"
-snappy="no"
+lzo=""
+snappy=""
 guest_agent=""
 guest_agent_with_vss="no"
 vss_win32_sdk=""
@@ -333,7 +333,7 @@ vte=""
 tpm="no"
 libssh2=""
 vhdx=""
-quorum="no"
+quorum=""
 
 # parse CC options first
 for opt do
@@ -1050,8 +1050,12 @@ for opt do
   ;;
   --disable-zlib-test) zlib="no"
   ;;
+  --disable-lzo) lzo="no"
+  ;;
   --enable-lzo) lzo="yes"
   ;;
+  --disable-snappy) snappy="no"
+  ;;
   --enable-snappy) snappy="yes"
   ;;
   --enable-guest-agent) guest_agent="yes"
@@ -1749,13 +1753,14 @@ if test "$lzo" != "no" ; then
 int main(void) { lzo_version(); return 0; }
 EOF
     if compile_prog "" "-llzo2" ; then
-        :
+        libs_softmmu="$libs_softmmu -llzo2"
+        lzo="yes"
     else
-        error_exit "lzo check failed" \
-            "Make sure to have the lzo libs and headers installed."
+        if test "$lzo" = "yes"; then
+            feature_not_found "liblzo2" "Install liblzo2 devel"
+        fi
+        lzo="no"
     fi
-
-    libs_softmmu="$libs_softmmu -llzo2"
 fi
 
 ##########################################
@@ -1767,13 +1772,14 @@ if test "$snappy" != "no" ; then
 int main(void) { snappy_max_compressed_length(4096); return 0; }
 EOF
     if compile_prog "" "-lsnappy" ; then
-        :
+        libs_softmmu="$libs_softmmu -lsnappy"
+        snappy="yes"
     else
-        error_exit "snappy check failed" \
-            "Make sure to have the snappy libs and headers installed."
+        if test "$snappy" = "yes"; then
+            feature_not_found "libsnappy" "Install libsnappy devel"
+        fi
+        snappy="no"
     fi
-
-    libs_softmmu="$libs_softmmu -lsnappy"
 fi
 
 ##########################################
@@ -2219,9 +2225,12 @@ if compile_prog "$quorum_tls_cflags" "$quorum_tls_libs" ; then
   libs_softmmu="$quorum_tls_libs $libs_softmmu"
   libs_tools="$quorum_tls_libs $libs_softmmu"
   QEMU_CFLAGS="$QEMU_CFLAGS $quorum_tls_cflags"
+  quorum="yes"
 else
-  echo "gnutls > 2.10.0 required to compile Quorum"
-  exit 1
+  if test "$quorum" = "yes"; then
+    feature_not_found "gnutls" "gnutls > 2.10.0 required to compile Quorum"
+  fi
+  quorum="no"
 fi
 fi
 

tests/qemu-iotests/081.out

@@ -45,5 +45,5 @@ wrote 10485760/10485760 bytes at offset 0
 10 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
 == checking that quorum is broken ==
-qemu-io: can't open device (null): Could not read image for determining its format: Input/output error
+qemu-io: can't open: Could not read image for determining its format: Input/output error
 *** done