Build fix: #undef O_TRUNC

Change-Id: I69c00ef15983c2934ce76429759ba3bbb3b14482
diff --git a/external/vulkancts/modules/vulkan/spirv_assembly/vktSpvAsmFloatControlsTests.cpp b/external/vulkancts/modules/vulkan/spirv_assembly/vktSpvAsmFloatControlsTests.cpp
index 9edc55b..40e2a53 100644
--- a/external/vulkancts/modules/vulkan/spirv_assembly/vktSpvAsmFloatControlsTests.cpp
+++ b/external/vulkancts/modules/vulkan/spirv_assembly/vktSpvAsmFloatControlsTests.cpp
@@ -36,6 +36,11 @@
 #include <limits>
 #include <fenv.h>
 
+// <string> may include fcntl.h which #defines O_TRUNC in musl
+#ifdef O_TRUNC
+#undef O_TRUNC
+#endif
+
 namespace vkt
 {
 namespace SpirVAssembly