Drop libsigchain from the system image.

It is now in the Runtime APEX and considered internal there.

Test: Flash and boot
Test: atest CtsCompilationTestCases CtsBionicTestCases
Bug: 118374951
Bug: 124293228
Change-Id: I33bb9c238d7db46795deb592c9d20fe6591c1654
diff --git a/core/Makefile b/core/Makefile
index 4def109..66e1fe1 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -2166,7 +2166,7 @@
 #   libicuuc.so
 #   libnativehelper.so  - cf_x86_phone-userdebug builds get this in system/lib/arm
 #   libprofile.so
-#   libsigchain.so
+#   libsigchain.so  - cf_x86_phone-userdebug builds get this in system/lib/arm
 #   libtombstoned_client.so
 APEX_MODULE_LIBS= \
   libadbconnection.so \
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index 6b9f4b4..6d161b4 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -165,7 +165,6 @@
     libradio_metadata \
     librtp_jni \
     libsensorservice \
-    libsigchain \
     libskia \
     libsonic \
     libsonivox \