add alpine edge CI build

Mainly to get a musl build in there.

Signed-off-by: Serge Hallyn <serge@hallyn.com>

.builds/alpine-edge.yml

@@ -0,0 +1,32 @@
+image: alpine/latest
+# apk add --update alpine-sdk
+packages:
+  - cmd:setcap
+  - autoconf
+  - automake
+  - byacc
+  - expect
+  - gettext
+  - gettext-dev
+  - gettext-lang
+  - libcap-dev
+  - libtool
+  - linux-pam-dev
+  - sed
+sources:
+  - https://github.com/shadow-maint/shadow
+tasks:
+  - build: |
+      cd shadow
+      ./autogen.sh --without-selinux --disable-man --disable-nls
+      grep ENABLE_ config.status
+  - tasks: |
+      cd shadow
+      cat /proc/self/uid_map
+      cat /proc/self/status
+      make
+      make DESTDIR=/tmp/shadow-inst install
+      sudo make install
+      #TODO - fix up the tests.  Let's merge what's here now as it
+      #at least tests build.
+      #(cd tests; sudo ./run_some || { cat testsuite.log; false; })