[Buildroot] [git commit branch/next] toolchain-external: make preinstall the default for custom toolchains

commit: http://git.buildroot.net/buildroot/commit/?id=701940770b658e25cfe7219e35e808ba62052843
branch: http://git.buildroot.net/buildroot/commit/?id=refs/heads/next

All the defconfig files used by the autobuilders that use
pre-installed external toolchains are making the assumption that the
default for a custom external toolchain is "pre-installed". We keep
this default for now, since changing it breaks the autobuilders.

Signed-off-by: Thomas Petazzoni <redacted>
---
 toolchain/toolchain-external/Config.in |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/toolchain/toolchain-external/Config.in b/toolchain/toolchain-external/Config.in
index 5c29ecd..e34802d 100644
--- a/toolchain/toolchain-external/Config.in
+++ b/toolchain/toolchain-external/Config.in

@@ -573,6 +573,10 @@ endchoice
 
 choice
 	prompt "Toolchain origin"
+	# Keep compatibility with old defconfig files that are using
+	# custom toolchains, and which are therefore assuming that
+	# "preinstalled" in the default choice.
+	default BR2_TOOLCHAIN_EXTERNAL_PREINSTALLED if BR2_TOOLCHAIN_EXTERNAL_CUSTOM
 
 config BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD
 	bool "Toolchain to be downloaded and installed"