utils/genrandconfig: fix BR2_TOOLCHAIN_BARE_METAL_BUILDROOT_ARCH

Commit b7232c51dd402afb361d7c310855e0bf5666958d added default setting
for bare-metal toolchain arch but unfortunately it used configlines.add
instead of configlines.append resulting in the following build failure:

/bin/sh: line 8: /home/autobuild/autobuild/instance-1/output-1/per-package/host-gcc-bare-metal/host/bin/-ar: No such file or directory

While at it, also append /n for consistency

Fixes: b7232c51dd402afb361d7c310855e0bf5666958d
 - http://autobuild.buildroot.org/results/95ac565653ddb5c14ec71470c32a34ad10b048cb

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

utils/genrandconfig

@@ -315,9 +315,9 @@ def fixup_config(sysinfo, configfile):
        'BR2_TOOLCHAIN_BUILDROOT=y' in configlines:
         return False
 
-    if 'BR2_TOOLCHAIN_BARE_METAL_BUILDROOT=y' in configlines:
-        configlines.remove('BR2_TOOLCHAIN_BARE_METAL_BUILDROOT_ARCH=""')
-        configlines.add('BR2_TOOLCHAIN_BARE_METAL_BUILDROOT_ARCH="microblazeel-xilinx-elf"')
+    if 'BR2_TOOLCHAIN_BARE_METAL_BUILDROOT=y\n' in configlines:
+        configlines.remove('BR2_TOOLCHAIN_BARE_METAL_BUILDROOT_ARCH=""\n')
+        configlines.append('BR2_TOOLCHAIN_BARE_METAL_BUILDROOT_ARCH="microblazeel-xilinx-elf"\n')
 
     if 'BR2_PACKAGE_AUFS_UTIL=y\n' in configlines and \
        'BR2_PACKAGE_AUFS_UTIL_VERSION=""\n' in configlines: