Allow only relative paths.

This commit makes the following changes:
* Disallow file:/// URIs
* Allow only relative paths in the .path field of build.zig.zon
* Remote now-unneeded shlwapi dependency

build.zig

@@ -336,7 +336,6 @@ pub fn build(b: *std.Build) !void {
                 artifact.linkSystemLibrary("version");
                 artifact.linkSystemLibrary("uuid");
                 artifact.linkSystemLibrary("ole32");
-                artifact.linkSystemLibrary("shlwapi");
             }
         }
     }
@@ -713,7 +712,6 @@ fn addStaticLlvmOptionsToExe(exe: *std.Build.Step.Compile) !void {
         exe.linkSystemLibrary("version");
         exe.linkSystemLibrary("uuid");
         exe.linkSystemLibrary("ole32");
-        exe.linkSystemLibrary("shlwapi");
     }
 }
 

lib/std/Uri.zig

@@ -150,7 +150,7 @@ pub fn parseWithoutScheme(text: []const u8) ParseError!Uri {
         std.debug.assert(reader.get().? == '/');
         std.debug.assert(reader.get().? == '/');
 
-        var authority = reader.readUntil(isAuthoritySeparator);
+        const authority = reader.readUntil(isAuthoritySeparator);
         if (authority.len == 0) {
             if (reader.peekPrefix("/")) break :a else return error.InvalidFormat;
         }

lib/std/os/windows.zig

@@ -30,7 +30,6 @@ pub const gdi32 = @import("windows/gdi32.zig");
 pub const winmm = @import("windows/winmm.zig");
 pub const crypt32 = @import("windows/crypt32.zig");
 pub const nls = @import("windows/nls.zig");
-pub const shlwapi = @import("windows/shlwapi.zig");
 
 pub const self_process_handle = @as(HANDLE, @ptrFromInt(maxInt(usize)));