Default to Arch target when _distro is empty or when using the PKGBUILD

Fixes https://github.com/Frogging-Family/linux-tkg/issues/104

PKGBUILD

@@ -13,8 +13,8 @@ plain '   :syNNdhNNhssssssssssssssshNNhdNNys:'
 plain '    /ssyhhhysssssssssssssssssyhhhyss/'
 plain '    .ossssssssssssssssssssssssssssso.'
 plain '   :sssssssssssssssssssssssssssssssss:'
-plain '  /sssssssssssssssssssssssssssssssssss/'
-plain ' :sssssssssssssoosssssssoosssssssssssss:'
+plain '  /sssssssssssssssssssssssssssssssssss/   Linux-tkg'
+plain ' :sssssssssssssoosssssssoosssssssssssss:        kernels'
 plain ' osssssssssssssoosssssssoossssssssssssso'
 plain ' osssssssssssyyyyhhhhhhhyyyyssssssssssso'
 plain ' /yyyyyyhhdmmmmNNNNNNNNNNNmmmmdhhyyyyyy/'
@@ -25,12 +25,11 @@ plain '       `-+shdNNNNNNNNNNNNNNNdhs+-`'
 plain '             `.-:///////:-.`'
 
 _where="$PWD" # track basedir as different Arch based distros are moving srcdir around
+_ispkgbuild="true"
 
 source "$_where"/customization.cfg # load default configuration from file
 source "$_where"/linux-tkg-config/prepare
 
-_distro="Arch"
-
 _tkg_initscript
 
 if [[ "$_sub" = rc* ]]; then

linux-tkg-config/prepare

@@ -9,7 +9,13 @@ ver510=rc1
 _tkg_initscript() {
   # Load external configuration file if present. Available variable values will overwrite customization.cfg ones.
   if [ -e "$_EXT_CONFIG_PATH" ]; then
-    source "$_EXT_CONFIG_PATH" && msg2 "External configuration file $_EXT_CONFIG_PATH will be used to override customization.cfg values." && msg2 ""
+    source "$_EXT_CONFIG_PATH" && msg2 "External configuration file $_EXT_CONFIG_PATH will be used to override customization.cfg values.\n"
+  fi
+
+  # Default to Arch
+  if [ -z "$_distro" ] || [ "$_ispkgbuild" = "true" ]; then
+    msg2 "Defaulting to Archlinux target\n"
+    _distro="Arch"
   fi
 
   # create build dir early