Toolchain environment override environment variable names now must be upper-case

[adamgreig]

In 0.3 and before #687, environment variable names for overrides such as AMARANTH_ENV_Diamond used the same case as the toolchain name (e.g., Diamond). After #687 the use of tool_env_var() inadvertently(?) causes all names to require upper-case, e.g. AMARANTH_ENV_DIAMOND. The upper-case name doesn't work in 0.3, and the previous mixed-case name no longer works.

[whitequark]

Thanks! I would be happy to review a PR fixing this issue.

[adamgreig]

Do you want to revert to the old behaviour or maybe make the environment variable names case-insensitive?

[whitequark]

make the environment variable names case-insensitive?

I think this would cause issues where you have both AMARANTH_ENV_DIAMOND and AMARANTH_ENV_Diamond, unfortunately :(

The impetus for #687 was to "[allow] Platform.toolchain to contain '+' or '-' characters.". Maybe we can fix just that instead?