tests: Skip network-dependent tests when the network is unreachable.

* tests/builders.scm (network-reachable?): New variable.
  ("url-fetch", "gnu-build"): Skip unless NETWORK-REACHABLE?.
* tests/derivations.scm (%coreutils): Check for network access.
  ("build-expression->derivation with one input"): Skip when %COREUTILS
  is #f.
* tests/guix-package.sh: Skip installation of GNU Make when the network
  is unreachable.
* tests/packages.scm ("GNU Make, bootstrap"): Likewise.
* tests/union.scm ("union-build"): Likewise.

1 files changed, 4 insertions, 2 deletions

diff --git a/tests/derivations.scm b/tests/derivations.scm
index 203bd9032f..46bab4e19d 100644
--- a/tests/derivations.scm
+++ b/tests/derivations.scm
@@ -290,8 +290,9 @@
 
 (define %coreutils
   (false-if-exception
-   (or (package-derivation %store %bootstrap-coreutils&co)
-       (nixpkgs-derivation "coreutils"))))
+   (and (getaddrinfo "www.gnu.org" "80" AI_NUMERICSERV)
+        (or (package-derivation %store %bootstrap-coreutils&co)
+            (nixpkgs-derivation "coreutils")))))
 
 (test-skip (if %coreutils 0 1))
 
@@ -385,6 +386,7 @@
            (and (equal? '(hello) (call-with-input-file one read))
                 (equal? '(world) (call-with-input-file two read)))))))
 
+(test-skip (if %coreutils 0 1))
 (test-assert "build-expression->derivation with one input"
   (let* ((builder    '(call-with-output-file %output
                         (lambda (p)