Add note about RAM issues to README.md

[jvdp1]

This is a note on how to avoid RAM issues during compilation on "low RAM" computers.

Fixes #217 and #281

[LKedward]

Looks great! Thanks @jvdp1 👍

[awvwgk]

The suggested instructions lead to the following error:

❯ cmake -B __build
-- The Fortran compiler identification is GNU 10.2.0
-- Detecting Fortran compiler ABI info
-- Detecting Fortran compiler ABI info - done
-- Check for working Fortran compiler: /usr/bin/f95 - skipped
-- Checking whether /usr/bin/f95 supports Fortran 90
-- Checking whether /usr/bin/f95 supports Fortran 90 - yes
-- Performing Test f18errorstop
-- Performing Test f18errorstop - Success
-- Performing Test f03rank
-- Performing Test f03rank - Success
-- Performing Test f03real128
-- Performing Test f03real128 - Success
-- Configuring done
-- Generating done
-- Build files have been written to: /home/awvwgk/projects/src/git/stdlib/__build
❯ cmake --build __build -DCMAKE_MAXIMUM_RANK=4
Unknown argument -DCMAKE_MAXIMUM_RANK=4
Usage: cmake --build <dir> [options] [-- [native-options]]
Options:
  <dir>          = Project binary directory to be built.
  --parallel [<jobs>], -j [<jobs>]
                 = Build in parallel using the given number of jobs. 
                   If <jobs> is omitted the native build tool's 
                   default number is used.
                   The CMAKE_BUILD_PARALLEL_LEVEL environment variable
                   specifies a default parallel level when this option
                   is not given.
  --target <tgt>..., -t <tgt>... 
                 = Build <tgt> instead of default targets.
  --config <cfg> = For multi-configuration tools, choose <cfg>.
  --clean-first  = Build target 'clean' first, then build.
                   (To clean only, use --target 'clean'.)
  --verbose, -v  = Enable verbose output - if supported - including
                   the build commands to be executed. 
  --             = Pass remaining options to the native tool.

[milancurcic]

Great, thank you. This note will be helpful. I added a suggestion to reword things a bit for clarity.

[jvdp1]

Great, thank you. This note will be helpful. I added a suggestion to reword things a bit for clarity.

Thank you @milancurcic for your suggestions. I accepted them. They are more general than mine, and make them still valid, even if PR #283 is accepted later.

[milancurcic]

Thank you @jvdp1!