glsl: align definition of _mesa_problem with the one in main/error.h

The ctx pointer not used by that function anyway, so const'ing it makes
no difference.

Signed-off-by: Eric Engestrom <eric@igalia.com>
Reviewed-by: David Heidelberg <david.heidelberg@collabora.com>
Reviewed-by: Marek Olšák <maraeo@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21557>

src/compiler/glsl/standalone_scaffolding.cpp

@@ -55,7 +55,7 @@ _mesa_warning(struct gl_context *ctx, const char *fmt, ...)
 }
 
 void
-_mesa_problem(struct gl_context *ctx, const char *fmt, ...)
+_mesa_problem(const struct gl_context *ctx, const char *fmt, ...)
 {
     va_list vargs;
     (void) ctx;

src/compiler/glsl/standalone_scaffolding.h

@@ -38,7 +38,7 @@ extern "C" void
 _mesa_warning(struct gl_context *ctx, const char *fmtString, ... );
 
 extern "C" void
-_mesa_problem(struct gl_context *ctx, const char *fmtString, ... );
+_mesa_problem(const struct gl_context *ctx, const char *fmtString, ... );
 
 extern "C" void
 _mesa_reference_shader_program_data(struct gl_shader_program_data **ptr,