Fix crypto/rand/urandom header guards for Fuchsia.

Fuchsia uses crypto/rand/fuchsia.c for CRYPTO_sysrand, and so must be
excluded from the Linux/Apple/POSIX variant.

Change-Id: Ide9f0aa2547d52ce0579cd0a1882b2cdcc7b95c6
Reviewed-on: https://boringssl-review.googlesource.com/13141
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/crypto/rand/urandom.c b/crypto/rand/urandom.c
index 2233203..3ccd940 100644
--- a/crypto/rand/urandom.c
+++ b/crypto/rand/urandom.c
@@ -16,7 +16,8 @@
 
 #include <openssl/rand.h>
 
-#if !defined(OPENSSL_WINDOWS) && !defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE)
+#if !defined(OPENSSL_WINDOWS) && !defined(OPENSSL_FUCHSIA) && \
+    !defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE)
 
 #include <assert.h>
 #include <errno.h>
@@ -328,4 +329,5 @@
   }
 }
 
-#endif  /* !OPENSSL_WINDOWS && !BORINGSSL_UNSAFE_DETERMINISTIC_MODE */
+#endif /* !OPENSSL_WINDOWS && !defined(OPENSSL_FUCHSIA) && \
+          !BORINGSSL_UNSAFE_DETERMINISTIC_MODE */