fix(rpm): add missing native build dependencies

COPR build failed on openssl-sys because openssl headers were not
available in the mock chroot. Adding:

- pkgconfig(openssl): fixes the immediate openssl-sys failure.
  Kept as a build dep because we plan to add optional mTLS between
  cortex and neuron, which requires native-tls/openssl at build time.
- cmake, gcc-c++: aws-lc-sys (pulled via rustls) compiles libcrypto
  via cmake and includes C++ sources. Would be the next failure after
  openssl.
- perl-interpreter: catchall for -sys crate build scripts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cortex.spec

@@ -13,6 +13,10 @@ ExclusiveArch:  x86_64
 BuildRequires:  rust >= 1.85
 BuildRequires:  cargo
 BuildRequires:  gcc
+BuildRequires:  gcc-c++
+BuildRequires:  cmake
+BuildRequires:  perl-interpreter
+BuildRequires:  pkgconfig(openssl)
 BuildRequires:  systemd-rpm-macros
 
 Requires(pre):  shadow-utils

neuron.spec

@@ -13,6 +13,10 @@ ExclusiveArch:  x86_64
 BuildRequires:  rust >= 1.85
 BuildRequires:  cargo
 BuildRequires:  gcc
+BuildRequires:  gcc-c++
+BuildRequires:  cmake
+BuildRequires:  perl-interpreter
+BuildRequires:  pkgconfig(openssl)
 BuildRequires:  systemd-rpm-macros
 
 Requires(pre):  shadow-utils