The musl libc also has pthread_getattr_np()

--- qtwebengine/src/3rdparty/chromium/third_party/WebKit/Source/platform/heap/ThreadState.cpp	2015-02-17 05:58:05.000000000 +0100
+++ qtwebengine/src/3rdparty/chromium/third_party/WebKit/Source/platform/heap/ThreadState.cpp	2015-06-05 02:29:15.253256411 +0200
@@ -54,7 +54,7 @@

 static void* getStackStart()
 {
-#if defined(__GLIBC__) || OS(ANDROID)
+#if defined(__GLIBC__) || OS(ANDROID) || OS(LINUX_MUSL)
     pthread_attr_t attr;
     if (!pthread_getattr_np(pthread_self(), &attr)) {
         void* base;