- Added SHARED define for building with -fPIC

diff --git a/library/Makefile b/library/Makefile
index 7983f7b..f9e5062 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -18,7 +18,9 @@
 # CFLAGS += -D_BSD_EXTENSION
 
 # To compile as a shared library:
-# CFLAGS += -fPIC
+ifdef SHARED
+CFLAGS += -fPIC
+endif
 
 SONAME=libpolarssl.so.0