[PATCH-for-6.0?] configure: Improve error message with specified meson path is not found

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

When building on a system where meson isn't available,
but installed manually as user pip package, we get:

  $ ../configure --meson=~/.local/bin/meson
  qemu/configure: line 6387: --version: command not found
  You are attempting to run "setup" which requires administrative
  privileges, but more information is needed in order to do so.
  Authenticating as "root"
  Password:

Improve the error message to something less scary:

  $ ../configure --meson=~/.local/bin/meson
  ERROR: Meson not found.  Use --meson=/path/to/meson (absolute path)

Actually in this case the fix is to use $HOME, not unexpanded ~:

  $ ../configure --meson=$HOME/.local/bin/meson
  The Meson build system
  Version: 0.56.99
  ...

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 configure | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 4f374b48890..088a82e3d86 100755
--- a/configure
+++ b/configure
@@ -1987,7 +1987,12 @@ case "$meson" in
     git | internal)
         meson="$python ${source_path}/meson/meson.py"
         ;;
-    *) meson=$(command -v "$meson") ;;
+    *)
+        meson=$(command -v "$meson")
+        if test -z "$meson"; then
+            error_exit "Meson not found.  Use --meson=/path/to/meson (absolute path)"
+        fi
+        ;;
 esac
 
 # Probe for ninja
-- 
2.26.3