Fix unit test build with OpenSSL and fix gn check failure

follow-up to
  https://webrtc-review.googlesource.com/c/src/+/358300
which links the unit tests against OpenSSL when building with that by using
  rtc_build_ssl = false
  rtc_ssl_root = "/usr/include/openssl"
as gn args which showed an additional gn check failure

BUG=None

Change-Id: Id3356f3e211509141f2a05f096f19a7b1b8eee9f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/358340
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#42720}

BUILD.gn

@@ -695,6 +695,12 @@ if (rtc_include_tests && !build_with_chromium) {
       ]
       shard_timeout = 900
     }
+
+    # Link unit tests against OpenSSL when not building with BoringSSL.
+    ldflags = []
+    if (!rtc_build_ssl) {
+      ldflags += [ "-lssl" ]
+    }
   }
 
   if (rtc_enable_google_benchmarks) {

rtc_base/BUILD.gn

@@ -18,6 +18,8 @@ if (!rtc_build_ssl) {
     assert(rtc_ssl_root != "",
            "You must specify rtc_ssl_root when rtc_build_ssl==0.")
     include_dirs = [ rtc_ssl_root ]
+
+    # Note: do not link against OpenSSL here.
   }
 }
 
@@ -1585,6 +1587,7 @@ rtc_library("ssl") {
       "openssl_identity.cc",
       "openssl_identity.h",
     ]
+    deps += [ ":crypto_random" ]
 
     configs += [ ":external_ssl_library" ]
   }