configure.ac: Fix --with-llvm-shared-libs

The third argument of AC_ARG_WITH is evaluated for any provided value,
not only on --with-, so it must not force-enable the feature
Also, setting $with_llvm_shared_libs in the opencl check was overriding
the user switch

https://bugs.freedesktop.org/show_bug.cgi?id=59851

Signed-off-by: Quentin Glidic <sardemff7+git@sardemff7.net>

configure.ac

@@ -611,7 +611,7 @@ AC_ARG_ENABLE([opencl],
          [enable OpenCL library NOTE: Enabling this option will also enable
           --with-llvm-shared-libs
           @<:@default=no@:>@])],
-   [enable_opencl="$enableval" with_llvm_shared_libs="$enableval"],
+   [],
    [enable_opencl=no])
 AC_ARG_ENABLE([xlib_glx],
     [AS_HELP_STRING([--enable-xlib-glx],
@@ -1629,8 +1629,13 @@ AC_ARG_ENABLE([gallium-llvm],
 AC_ARG_WITH([llvm-shared-libs],
     [AS_HELP_STRING([--with-llvm-shared-libs],
         [link with LLVM shared libraries @<:@default=disabled@:>@])],
-    [with_llvm_shared_libs=yes],
+    [],
     [with_llvm_shared_libs=no])
+AS_IF([test x$enable_opencl = xyes],
+    [
+        AC_MSG_WARN([OpenCL required, forcing LLVM shared libraries])
+        with_llvm_shared_libs=yes
+    ])
 
 AC_ARG_WITH([llvm-prefix],
     [AS_HELP_STRING([--with-llvm-prefix],