build: Conditional enabling of osx-private-key-storage compilation

Makefile.am now contains a condition to enable/disable compilation of
osx-private-key-storage, instead of relying on define in the key storage
implementation.

Change-Id: I4a2079d99cd515c744cbe8f90a34a39e5c8197fa
diff --git a/Makefile.am b/Makefile.am
index 850d034..951e891 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -103,7 +103,6 @@
   src/security/identity/identity-storage.cpp \
   src/security/identity/memory-identity-storage.cpp \
   src/security/identity/memory-private-key-storage.cpp \
-  src/security/identity/osx-private-key-storage.cpp \
   src/security/key-chain.cpp \
   src/security/policy/no-verify-policy-manager.cpp \
   src/security/policy/self-verify-policy-manager.cpp \
@@ -120,6 +119,12 @@
   src/util/string-helper.hpp \
   src/util/time.hpp
 
+if HAVE_OSX_SECURITY
+  libndn_cpp_la_SOURCES += src/security/identity/osx-private-key-storage.cpp
+else
+  EXTRA_DIST = src/security/identity/osx-private-key-storage.cpp
+endif
+
 libndn_cpp_la_LIBADD  = @OPENSSL_LIBS@ @CRYPTOPP_LIBS@ @OSX_SECURITY_LIBS@
 libndn_cpp_la_LDFLAGS = @OPENSSL_LDFLAGS@  @CRYPTOPP_LDFLAGS@ @SQLITE3_LDFLAGS@ @BOOST_LDFLAGS@
 libndn_cpp_la_CFLAGS  = @OPENSSL_INCLUDES@ @CRYPTOPP_INCLUDES@ @SQLITE3_CFLAGS@  @BOOST_CPPFLAGS@