Don't linkcheck external web links

This can block PR CI yet remain unactionable for the contributor, since
this is subject to network conditions and availability of the servers
hosting the external web links.

Author: jieyouxu

book.toml

@@ -27,31 +27,11 @@ level = 0
 
 [output.linkcheck]
 command = "ci/linkcheck.sh"
-follow-web-links = true
-exclude = [
-    "crates\\.io",
-    "gcc\\.godbolt\\.org",
-    "youtube\\.com",
-    "youtu\\.be",
-    "dl\\.acm\\.org",
-    "cs\\.bgu\\.ac\\.il",
-    "www\\.amazon\\.com",
-    "www\\.rustaceans\\.org",
-    "play\\.rust-lang\\.org",
-    "tomlee\\.co",
-    "marketplace\\.visualstudio\\.com",
-    "objects\\.githubusercontent\\.com",
-    # The bug listing URL works only if an user is logged in, otherwise one gets 404.
-    "github\\.com/issues\\?q=.*",
-    # Similarly 500 is sometimes returned here.
-    "github\\.com/rust-lang/rust/pulls\\?q=.*",
-    # 401 is returned here for unknown reason
-    "github\\.com/wesleywiser/rustc-bootstrap-wpa-analysis",
-    # Handle: connection closed before message completed
-    "microsoft\\.com/en-us/research/publication/",
-    # 500 is returned for HEAD request
-    "code\\.visualstudio\\.com/docs/editor/tasks",
-]
+# Don't follow external web links, because that is subject to network conditions
+# and the server conditions of the external web links. These are beyond our
+# control and really should not block PR CI.
+follow-web-links = false
+
 # The scheduled CI runs every day and so we need to reuse a part of the cache
 # in order to face "Server returned 429 Too Many Requests" errors for github.com.
 cache-timeout = 90000