compiler/glsl: Use mutex lock while freeing up mem_ctx

builtin_builder::~builtin_builder() and builtin_builder::release()
are running into race condition. This leads lightsmark to crash at
the end because both calls ralloc_free which mutates the arguments state

This patch fixes lightsmark2008 crash

Fixes: e4da8b9c33 ("mesa/compiler: rework tear down of builtin/types")

Reviewed-by: Charmaine Lee <charmainel@vmware.com>
Reviewed-by: Neha Bhende <bhenden@vmware.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-by: Neha Bhende <bhenden@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11385>
(cherry picked from commit eb272f6571)

.pick_status.json

@@ -787,7 +787,7 @@
         "description": "compiler/glsl: Use mutex lock while freeing up mem_ctx",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "e4da8b9c331cc3ae1b86b3a7860231e202463db0"
     },

src/compiler/glsl/builtin_functions.cpp

@@ -90,6 +90,8 @@
 
 using namespace ir_builder;
 
+static mtx_t builtins_lock = _MTX_INITIALIZER_NP;
+
 /**
  * Availability predicates:
  *  @{
@@ -1296,7 +1298,15 @@ builtin_builder::builtin_builder()
 
 builtin_builder::~builtin_builder()
 {
+   mtx_lock(&builtins_lock);
+
    ralloc_free(mem_ctx);
+   mem_ctx = NULL;
+
+   ralloc_free(shader);
+   shader = NULL;
+
+   mtx_unlock(&builtins_lock);
 }
 
 ir_function_signature *
@@ -7753,7 +7763,6 @@ builtin_builder::_helper_invocation()
 
 /* The singleton instance of builtin_builder. */
 static builtin_builder builtins;
-static mtx_t builtins_lock = _MTX_INITIALIZER_NP;
 static uint32_t builtin_users = 0;
 
 /**