install/encrypt: resolve libgcc_s and the OpenSSL modules dir at build time

Gentoo keeps libgcc_s.so.1 under the active gcc's libdir (or in
/usr/lib64 from sys-libs/libgcc on clang systems) and the OpenSSL
providers under /usr/$(get_libdir)/ossl-modules, so the /usr/lib paths
hardcoded here are never found. Ask the dynamic loader cache and openssl
itself instead, which also follows toolchain and libdir changes.

--- a/install/encrypt
+++ b/install/encrypt
@@ -20,10 +20,10 @@ build() {
         '95-dm-notify.rules'
 
     # cryptsetup calls pthread_create(), which dlopen()s libgcc_s.so.1
-    add_binary '/usr/lib/libgcc_s.so.1'
+    add_binary "$(ldconfig -p | awk '/[[:space:]]libgcc_s\.so\.1 \(/ { print $NF; exit }')" /usr/lib/libgcc_s.so.1
 
     # cryptsetup loads the legacy provider which is required for whirlpool
-    add_binary '/usr/lib/ossl-modules/legacy.so'
+    add_binary "$(openssl version -m | sed 's/.*"\(.*\)"/\1/')/legacy.so"
 
     add_runscript
 }