Fix installation command

`--build-option` is not the correct config setting to use; we need
`--global-option`.

Ref #1679.

README.md

@@ -130,7 +130,7 @@ CUDA and C++ extensions via
 git clone https://github.com/NVIDIA/apex
 cd apex
 # if pip >= 23.1 (ref: https://pip.pypa.io/en/stable/news/#v23-1) which supports multiple `--config-settings` with the same key... 
-pip install -v --disable-pip-version-check --no-cache-dir --no-build-isolation --config-settings "--build-option=--cpp_ext" --config-settings "--build-option=--cuda_ext" ./
+pip install -v --disable-pip-version-check --no-cache-dir --no-build-isolation --config-settings "--global-option=--cpp_ext" --config-settings "--global-option=--cuda_ext" ./
 # otherwise
 pip install -v --disable-pip-version-check --no-cache-dir --no-build-isolation --global-option="--cpp_ext" --global-option="--cuda_ext" ./
 ```
@@ -148,7 +148,7 @@ A Python-only build omits:
 
 
 ### [Experimental] Windows
-`pip install -v --disable-pip-version-check --no-cache-dir --no-build-isolation --config-settings "--build-option=--cpp_ext" --config-settings "--build-option=--cuda_ext" .` may work if you were able to build Pytorch from source
+`pip install -v --disable-pip-version-check --no-cache-dir --no-build-isolation --config-settings "--global-option=--cpp_ext" --config-settings "--global-option=--cuda_ext" .` may work if you were able to build Pytorch from source
 on your system. A Python-only build via `pip install -v --no-cache-dir .` is more likely to work.  
 If you installed Pytorch in a Conda environment, make sure to install Apex in that same environment.