[Qemu-block] [PATCH 3/6] configure: Link test before auto-enabling the libusb library

[Philippe Mathieu-Daudé]

Similarly to commit a73e82ef912, test the library links correctly
before considering it as usable.

This fixes using ./configure --static on Ubuntu 18.04:

  $ make subdir-aarch64-softmmu
  [...]
    LINK    aarch64-softmmu/qemu-system-aarch64
  /usr/bin/ld: cannot find -ludev
  collect2: error: ld returned 1 exit status
  Makefile:204: recipe for target 'qemu-system-aarch64' failed
  make[1]: *** [qemu-system-aarch64] Error 1

  $ fgrep udev config-host.mak
  LIBUSB_LIBS=-lusb-1.0 -ludev -pthread

  $ lsb_release -cri
  Distributor ID: Ubuntu
  Release:        18.04
  Codename:       bionic

Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
---
 configure | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 3428adb75b..e2511df1e3 100755
--- a/configure
+++ b/configure
@@ -4898,9 +4898,23 @@ fi
 # check for libusb
 if test "$libusb" != "no" ; then
     if $pkg_config --atleast-version=1.0.13 libusb-1.0; then
-        libusb="yes"
         libusb_cflags=$($pkg_config --cflags libusb-1.0)
-        libusb_libs=$($pkg_config --libs libusb-1.0)
+        if test "$static" = "yes"; then
+            libusb_libs=$($pkg_config --libs --static libusb-1.0)
+        else
+            libusb_libs=$($pkg_config --libs libusb-1.0)
+        fi
+        # Packaging for the static libraries is not always correct.
+        # At least ubuntu 18.04 ships only shared libraries.
+        write_c_skeleton
+        if ! compile_prog "$libusb_cflags" "$libusb_libs" ; then
+            if test "$libusb" = "yes" ; then
+              error_exit "libusb check failed."
+            fi
+            libusb="no"
+        else
+            libusb="yes"
+        fi
     else
         if test "$libusb" = "yes"; then
             feature_not_found "libusb" "Install libusb devel >= 1.0.13"
-- 
2.20.1