Include also ARM build of protoc in nuget package (#21568)

Closes #21568

COPYBARA_INTEGRATE_REVIEW=#21568 from FooRider:nuget-include-linuxaarch64 c6d5853
PiperOrigin-RevId: 755009744

Author: FooRider

csharp/Google.Protobuf.Tools.nuspec

@@ -20,6 +20,7 @@
     <file src="protoc/windows_x64/protoc.exe" target="tools/windows_x64/protoc.exe"/>
     <file src="protoc/linux_x86/protoc" target="tools/linux_x86/protoc"/>
     <file src="protoc/linux_x64/protoc" target="tools/linux_x64/protoc"/>
+    <file src="protoc/linux_aarch64/protoc" target="tools/linux_aarch64/protoc"/>
     <file src="protoc/macosx_x64/protoc" target="tools/macosx_x64/protoc"/>
     <file src="src/google/protobuf/any.proto" target="tools/google/protobuf"/>
     <file src="src/google/protobuf/api.proto" target="tools/google/protobuf"/>

csharp/Google.Protobuf.Tools.targets

@@ -3,6 +3,7 @@
         <protoc_tools>$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)/../tools/'))</protoc_tools>
         <protoc_linux64>$([System.IO.Path]::GetFullPath('$(protoc_tools)/linux_x64/protoc'))</protoc_linux64>
         <protoc_linux86>$([System.IO.Path]::GetFullPath('$(protoc_tools)/linux_x86/protoc'))</protoc_linux86>
+        <protoc_linuxaarch64>$([System.IO.Path]::GetFullPath('$(protoc_tools)/linux_aarch64/protoc'))</protoc_linuxaarch64>
         <protoc_macosx64>$([System.IO.Path]::GetFullPath('$(protoc_tools)/macosx_x64/protoc'))</protoc_macosx64>
         <protoc_macosx86>$([System.IO.Path]::GetFullPath('$(protoc_tools)/macosx_x86/protoc'))</protoc_macosx86>
         <protoc_windows64>$([System.IO.Path]::GetFullPath('$(protoc_tools)/windows_x64/protoc.exe'))</protoc_windows64>

csharp/build_tools.sh

@@ -16,12 +16,13 @@ fi
 
 VERSION_NUMBER=$1
 # <directory name> <binary file name> pairs.
-declare -a FILE_NAMES=(          \
-  windows_x86 windows-x86_32.exe \
-  windows_x64 windows-x86_64.exe \
-  macosx_x64  osx-x86_64.exe     \
-  linux_x86   linux-x86_32.exe   \
-  linux_x64   linux-x86_64.exe   \
+declare -a FILE_NAMES=(             \
+  windows_x86   windows-x86_32.exe  \
+  windows_x64   windows-x86_64.exe  \
+  macosx_x64    osx-x86_64.exe      \
+  linux_x86     linux-x86_32.exe    \
+  linux_x64     linux-x86_64.exe    \
+  linux_aarch64 linux-aaarch_64.exe \
 )
 
 set -e