delete link test "static_lib_as_system_lib"

I disagree with this behavior and will be reverting the changes
corresponding to this test case.

Also this test case unnecessarily uses a .c file when a .zig file would
be preferred, and has a problematic dependency on the install step,
preventing this test case from playing nicely with the cache.

Author: andrewrk

test/link.zig

@@ -20,10 +20,6 @@ pub const cases = [_]Case{
         .build_root = "test/link/interdependent_static_c_libs",
         .import = @import("link/interdependent_static_c_libs/build.zig"),
     },
-    //.{
-    //    .build_root = "test/link/static_lib_as_system_lib",
-    //    .import = @import("link/static_lib_as_system_lib/build.zig"),
-    //},
 };
 
 //pub fn addCases(cases: *Standalone) void {