docs: getting started guide 3rd party toolchains fixes

Using 3rd Party Toolchains page find out that warning message
can be moved to the top of the page.
Add Windows example in OneAPI.
Style fixing.

Signed-off-by: Maksim Masalski <[email protected]>

Author: Maksim Masalski

doc/getting_started/toolchain_3rd_party_x_compilers.rst

@@ -11,13 +11,16 @@ external organization. Several of these are available.
 GNU ARM Embedded
 ****************
 
+   .. warning::
+
+      Do not install the toolchain into a path with spaces.
+
 #. Download and install a `GNU ARM Embedded`_ build for your operating system
    and extract it on your file system.
 
-   .. warning::
+   .. note::
 
-      Do not install the toolchain into a path with spaces. On
-      Windows, we'll assume you install into the directory
+      On Windows, we'll assume you install into the directory
       :file:`C:\\gnu_arm_embedded`.
 
    .. warning::
@@ -44,7 +47,7 @@ GNU ARM Embedded
       $ echo $GNUARMEMB_TOOLCHAIN_PATH
       /home/you/Downloads/gnu_arm_embedded
 
-      # Windows
+      # Windows:
       > echo %ZEPHYR_TOOLCHAIN_VARIANT%
       gnuarmemb
       > echo %GNUARMEMB_TOOLCHAIN_PATH%
@@ -58,7 +61,7 @@ GNU ARM Embedded
       - Set :envvar:`ZEPHYR_TOOLCHAIN_VARIANT` to ``gnuarmemb``.
       - Set :envvar:`GNUARMEMB_TOOLCHAIN_PATH` to the brew installation directory (something like ``/usr/local``)
 
-Intel oneApi Toolkits
+Intel oneAPI Toolkit
 *********************
 
 #. Download `Intel oneAPI Base Toolkit
@@ -67,9 +70,13 @@ Intel oneApi Toolkits
 #. Assuming the toolkit is installed in ``/opt/intel/oneApi``, set environment
    using::
 
+        # Linux, macOS:
         export ONEAPI_TOOLCHAIN_PATH=/opt/intel/oneapi
         source $ONEAPI_TOOLCHAIN_PATH/compiler/latest/env/vars.sh
 
+        # Windows:
+        > set ONEAPI_TOOLCHAIN_PATH=C:\Users\Intel\oneapi
+
    To setup the complete oneApi environment, use::
 
         source  /opt/intel/oneapi/setvars.sh
@@ -106,7 +113,7 @@ DesignWare ARC MetaWare Development Toolkit (MWDT)
       $ echo $ARCMWDT_TOOLCHAIN_PATH
       /home/you/ARC/MWDT_2019.12/
 
-      # Windows
+      # Windows:
       > echo %ZEPHYR_TOOLCHAIN_VARIANT%
       arcmwdt
       > echo %ARCMWDT_TOOLCHAIN_PATH%