src/CMakeLists.txt: fix static build with openssl

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

src/CMakeLists.txt

@@ -29,7 +29,11 @@ set(UHTTPD_HAVE_MBEDTLS_CONFIG 0)
 if(NOT UHTTPD_SSL_SUPPORT)
     set(UHTTPD_SSL_SUPPORT_CONFIG 0)
 else()
-    find_package(OpenSSL)
+    find_package(PkgConfig QUIET)
+    pkg_check_modules(OPENSSL QUIET openssl)
+    if (NOT OPENSSL_FOUND)
+        find_package(OpenSSL)
+    endif()
     find_package(WolfSSL)
     find_package(MbedTLS)