Fix: always use getrandom on Linux and Android >= 28 (#16478)

Crystal < 1.7 don't support calling the `has_method?` macro from the top level. We already assume the `getrandom` libc function to be available on every Linux targets except Android 24 to 27 for which we now check the actual API version instead of the libc fun.

Co-authored-by: Johannes Müller <straightshoota@gmail.com>

Author: ysbaddaden

src/crystal/system/random.cr

@@ -12,15 +12,10 @@ end
 
 {% if flag?(:wasi) %}
   require "./wasi/random"
-{% elsif flag?(:linux) %}
-  require "c/sys/random"
-  \{% if LibC.has_method?(:getrandom) %}
-    require "./unix/getrandom"
-  \{% else %}
-    require "./unix/urandom"
-  \{% end %}
 {% elsif flag?(:bsd) || flag?(:darwin) %}
   require "./unix/arc4random"
+{% elsif flag?(:linux) && (!flag?(:android) || LibC::ANDROID_API >= 28) %}
+  require "./unix/getrandom"
 {% elsif flag?(:unix) %}
   require "./unix/urandom"
 {% elsif flag?(:win32) %}