Tell GCC that sometimes we have to build deprecated functions.

We're the C library. Nothing could be more deprecated.

bionic/libc/bionic/pthread_cond.cpp:243:10: error: 'int pthread_cond_timedwait_relative_np(pthread_cond_t*, pthread_mutex_t*, const timespec*)' is deprecated (declared at bionic/libc/bionic/pthread_cond.cpp:227): use pthread_cond_timedwait instead [-Werror=deprecated-declarations]
   return pthread_cond_timedwait_relative_np(cond_interface, mutex, &ts);
          ^
bionic/libc/bionic/pthread_cond.cpp:243:71: error: 'int pthread_cond_timedwait_relative_np(pthread_cond_t*, pthread_mutex_t*, const timespec*)' is deprecated (declared at bionic/libc/bionic/pthread_cond.cpp:227): use pthread_cond_timedwait instead [-Werror=deprecated-declarations]
   return pthread_cond_timedwait_relative_np(cond_interface, mutex, &ts);
                                                                       ^

Change-Id: Idb3d445e053c44180773f59774df19b324f6817f
diff --git a/libc/Android.mk b/libc/Android.mk
index ffa8a27..e51878d 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -575,6 +575,7 @@
 libc_common_cflags := \
     -D_LIBC=1 \
     -Wall -Wextra -Wunused \
+    -Wno-deprecated-declarations \
 
 use_clang := $(USE_CLANG_PLATFORM_BUILD)