contrib: drop os marker files, check Makefile instead

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

contrib/alpine/Makefile.am

@@ -1,5 +1,5 @@
 SUBDIRS    = finit.d
 docsdir   := @docdir@/contrib/alpine
-docs_DATA  = README.md finit.conf alpine-release build.sh install.sh rc.local
+docs_DATA  = README.md finit.conf build.sh install.sh rc.local
 EXTRA_DIST = $(docs_DATA)
 

contrib/alpine/alpine-release

@@ -1 +0,0 @@
-3.6.2

contrib/alpine/install.sh

@@ -8,7 +8,8 @@ if [ "x`id -u`" != "x0" ]; then
 fi
 
 # Adjust base directory
-if [ -e alpine-release ]; then
+grep -q alpine Makefile 2>/dev/null
+if [ $? -eq 0 ]; then
     cd ../..
 elif [ ! -e configure.ac ]; then
     echo "*** Please run this script from the Finit base directory."