rusticl: add -cl-std only when it's not defined

This fixes piglit "Invalid CL Version Declaration" test.

Fixes: fc30fe2c11 ("rusticl/kernel: add missing preprocessor definitions")

Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: David Heidelberg <david@ixit.cz>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29638>

src/gallium/drivers/llvmpipe/ci/llvmpipe-rusticl-fails.txt

@@ -26,11 +26,6 @@ api@clgetkernelarginfo,Fail
 # Failed (error code: CL_SUCCESS): Trigger CL_LINK_PROGRAM_FAILURE if there is a failure to link the compiled binaries and/or libraries.
 api@cllinkprogram,Fail
 
-# input.cl:31:2: error: use of undeclared identifier 'double2'; did you mean 'double'?
-# [...]
-# Program built when it should have failed: CL_SUCCESS
-program@build@fail@invalid-version-declaration,Fail
-
 # "input.cl:8:10: fatal error: 'include_test.h' file not found"
 # build-piglit.sh removes all the *.[ch] files from the piglit tree, so it's a Mesa CI bug.
 program@build@include-directories,Fail

src/gallium/frontends/rusticl/core/program.rs

@@ -298,7 +298,7 @@ pub struct ProgramDevBuild {
 
 fn prepare_options(options: &str, dev: &Device) -> Vec<CString> {
     let mut options = options.to_owned();
-    if !options.contains("-cl-std=CL") {
+    if !options.contains("-cl-std=") {
         options.push_str(" -cl-std=CL");
         options.push_str(dev.clc_version.api_str());
     }