Pick correct toolchain for Linux builds

[kneth]

What, How & Why?

This closes #6082

In order to see which GLIBC versions a binary is depending on, I have used the following command:

objdump -T realm.node  | grep GLIBC_ | awk '{ print $5 }' | tr -d "()GLIBC_" | sort | uniq

I have examined the binaries distributed with v12.0.0, and the following list is produced:

2.10
2.14
2.16
2.17
2.2.5
2.3
2.3.2
2.3.4
2.32
2.33
2.34
2.4
2.7
2.9

Moreover I have built the binary locally using this pull request, and the list is

2.10
2.12
2.14
2.17
2.2.5
2.3
2.3.2
2.3.4
2.7
2.9

Conclusion: this PR is producing a binary which depends on GLIBC v2.17 which is compatible with RHEL 7 and CentOS 7.

Fun read - and inspiration to the objdump command: Make binaries portable across linux distros

☑️ ToDos

• 📝 Changelog entry
• 📝 Compatibility label is updated or copied from previous entry
• 📝 Update COMPATIBILITY.md
• 🚦 Tests
• 📦 Updated internal package version in consuming package.jsons (if updating internal packages)
• 📱 Check the React Native/other sample apps work if necessary
• 💥 Breaking label has been applied or is not necessary