Enable build on OpenPOWER systems (ppc64le)

Fix overly simplistic architecture check.

We have been using Zimbra on POWER in production for around one year with this modification.  Zimbra has been fast and reliable on these platforms.

build.pl

@@ -772,6 +772,12 @@ ()
    return "x86_64"
      if ( $b_os =~ /RHEL[0-9]+_64/ || $b_os =~ /CENTOS[0-9]+_64/ );
 
+   return "ppc64el"
+     if ( ( (POSIX::uname)[4] eq "ppc64le" ) and ( $b_os =~ /UBUNTU[0-9]+/) );
+
+   return "ppc64le"
+     if ( ( (POSIX::uname)[4] eq "ppc64le" ) and ( $b_os =~ /RHEL[0-9]+_64/ || $b_os =~ /CENTOS[0-9]+_64/ ) );
+
    Die("Could not determine BUILD_ARCH");
 }
 
@@ -785,6 +791,13 @@ ()
    return "r$1"
      if ( $b_os =~ /RHEL([0-9]+)_/ || $b_os =~ /CENTOS([0-9]+)_/ );
 
+    # Fallback for non-x86 architectures
+   return "u$1"
+     if ( $b_os =~ /UBUNTU([0-9]+)/ );
+
+   return "r$1"
+     if ( $b_os =~ /RHEL([0-9]+)/ || $b_os =~ /CENTOS([0-9]+)/ );
+
    Die("Could not determine PKG_OS_TAG");
 }