More robust env.sh | Fix conda activate if in subshell

[abejgonzalez]

env.sh is now not appended too. Instead, it replaces its text like how conda init bash replaces text in a comment block. Additionally, fixes the way conda activate is called so that it works on any system that has conda setup properly (whether or not conda is in the PATH as a function or not).

Code adapted from: https://github.com/conda/conda/blob/e69b2353c2f14fbfc9fd3aa448ebc991b28ca136/conda/core/initialize.py and from https://github.com/firesim/firesim/blob/70f5ac37ed74e7411ec5a77e422339b880f79a54/build-setup-nolog.sh#L121

Related PRs / Issues:
Fixes #1651.

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• RTL change
• Software change (RISC-V software)
• Build system change
• Other

Contributor Checklist:

• Did you set main as the base branch?
• Is this PR's title suitable for inclusion in the changelog and have you added a changelog:<topic> label?
• Did you state the type-of-change/impact?
• Did you delete any extraneous prints/debugging code?
• Did you mark the PR with a changelog: label?
• (If applicable) Did you update the conda .conda-lock.yml file if you updated the conda requirements file?
• (If applicable) Did you add documentation for the feature?
• (If applicable) Did you add a test demonstrating the PR?

• (If applicable) Did you mark the PR as Please Backport?

[jerryz123]

LGTM, but perhaps someone more familiar with Conda should review as well

[abejgonzalez]

LGTM, but perhaps someone more familiar with Conda should review as well

The extra conda lines were merged into / taken from FireSim so they should already be fairly robust. The replacement stuff should be pretty self-explanatory.

I'll go ahead and merge and we can fix it along the way if things break.