bitbake.conf/toolchain-shar-extract: Use en_US.UTF-8 as locale

Under python 3, if we spawn python processes, we need to have a UTF-8 locale, else python's file access methods will use ascii. You can't change that mode once the interpreter is started so we have to ensure a locale is set. Ideally we'd use C.UTF-8 since OE already forces the C locale but not all distros support that and we need to set something so en_US.UTF-8 seems as standard we we can get.

This matches the change in bitbake revision 8902c29638411d312e6fc4a197707e5742652e15

Also set this into the environment used when installing SDKs since python can be run and we need to ensure we use a standardised locale which is available from things like buildtools-tarball.

index 8a84e53..acef30b 100644
@@ -488,7 +488,7 @@ export BUILD_NM = "${BUILD_PREFIX}nm"
 export MAKE = "make"
 EXTRA_OEMAKE = ""
 EXTRA_OECONF = ""
-export LC_ALL = "C"
+export LC_ALL = "en_US.UTF-8"
 
 ##################################################################
 # Patch handling.

index 397be11..d1ce86d 100644
@@ -1,6 +1,7 @@
 #!/bin/sh
 
 [ -z "$ENVCLEANED" ] && exec /usr/bin/env -i ENVCLEANED=1 HOME="$HOME" \
+	LC_ALL=en_US.UTF-8 \
 	http_proxy="$http_proxy" https_proxy="$https_proxy" ftp_proxy="$ftp_proxy" \
 	no_proxy="$no_proxy" all_proxy="$all_proxy" GIT_PROXY_COMMAND="$GIT_PROXY_COMMAND" "$0" "$@"
 [ -f /etc/environment ] && . /etc/environment