Fix build for UCLIBC platforms

src/core/SkVarAlloc.cpp

Index: src/core/SkVarAlloc.cpp
diff --git a/src/core/SkVarAlloc.cpp b/src/core/SkVarAlloc.cpp
index ba5d6f50b05a12e83aec99bed1a7ff636c299948..88bd17028fbe19156e448e3f066cb2b0230421ca 100644
--- a/src/core/SkVarAlloc.cpp
+++ b/src/core/SkVarAlloc.cpp
@@ -47,7 +47,7 @@ void SkVarAlloc::makeSpace(size_t bytes, unsigned flags) {
 
 #if defined(SK_BUILD_FOR_MAC)
     SkASSERT(alloc == malloc_good_size(alloc));
-#elif defined(SK_BUILD_FOR_UNIX)
+#elif defined(SK_BUILD_FOR_UNIX) && !defined(__UCLIBC__)
     // TODO(mtklein): tune so we can assert something like this
     //SkASSERT(alloc == malloc_usable_size(fBlock));
 #endif
@@ -56,7 +56,7 @@ void SkVarAlloc::makeSpace(size_t bytes, unsigned flags) {
 static size_t heap_size(void* p) {
 #if defined(SK_BUILD_FOR_MAC)
     return malloc_size(p);
-#elif defined(SK_BUILD_FOR_UNIX)
+#elif defined(SK_BUILD_FOR_UNIX) && !defined(__UCLIBC__)
     return malloc_usable_size(p);
 #elif defined(SK_BUILD_FOR_WIN32)
     return _msize(p);