README: Fix non-existent iconv in macOS instruction

[Krinkle]

Follows-up 22e444c (GH-18670). There is currently no formula called "iconv" at https://brew.sh/ or https://github.com/Homebrew/homebrew-core/.

$ brew install iconv
Warning: No available formula with the name "iconv". Did you mean icon or cconv?

There is one called libiconv, however.

https://formulae.brew.sh/formula/libiconv

[DanielEScherzer]

@Krinkle can you confirm that libiconv does what the iconv dependency was meant to do, and that the updated instructions allow for building PHP on macos?

CC @xepozz who added the documentation

[xepozz]

Agree this is correct version. Looks like I copied from the linux instruction

[DanielEScherzer]

Thanks, will merge after confirmation that the updated docs do indeed allow for build PHP

[Krinkle]

Before installing libiconv, ./configure --enable-debug failed. So, whatever the correct one is, I didn't already have it installed by chance.

After installing libiconv, is still failed. Apparently, /opt/homebrew/opt/libiconv/bin as part of my PATH is insufficient. The script then tells me to use --with-iconv. Calling it with ./configure --enable-debug --with-iconv=/opt/homebrew/opt/libiconv works properly on macOS for me, and make -j8 && make TEST_PHP_ARGS=-j8 test now passes.

[DanielEScherzer]

After installing libiconv, is still failed. Apparently, /opt/homebrew/opt/libiconv/bin as part of my PATH is insufficient. The script then tells me to use --with-iconv. Calling it with ./configure --enable-debug --with-iconv=/opt/homebrew/opt/libiconv works properly on macOS for me, and make -j8 && make TEST_PHP_ARGS=-j8 test now passes.

Okay, do you want to add that part to the documentation?