Update tools intro section to capture new requirements for ARMC6 tranisition

Author: SenRamakri

docs/tools/tools_intro.md

@@ -27,14 +27,15 @@ Mbed OS 5 can be built with various toolchains. The currently supported versions
 
 ##### Arm Mbed Online Compiler
 
-The Mbed Online Compiler is our in-house IDE, and should be familiar to anyone who's been working with Mbed for a while. It switches the backing toolchain based on the architecture version:
+The Mbed Online Compiler is our in-house IDE, and should be familiar to anyone who's been working with Mbed for a while. It switches the backing toolchain based on the architecture version as in the table below.
+
 
 | Architecture version | Compiler |
 |----                  |----           |
-| Arm v6M       | Arm Compiler 6.11 |
-| Arm v7M       | Arm Compiler 6.11 |
-| Arm v7A       | Arm Compiler 6.11 |
-| Arm v8M       | Arm Compiler 6.11 |
+| Arm v6M       | `Arm Compiler 6.11` or `Arm Compiler 5.06 update 6` based on ARM toolchain supported by target (see `supported_toolchains` in [Adding and configuring targets](../reference/configuration/mbed_targets.html#)) |
+| Arm v7M       | `Arm Compiler 6.11` or `Arm Compiler 5.06 update 6` based on ARM toolchain supported by target (see `supported_toolchains` in [Adding and configuring targets](../reference/configuration/mbed_targets.html#)) |
+| Arm v7A       | `Arm Compiler 6.11` |
+| Arm v8M       | `Arm Compiler 6.11` |
 
 For more information, please see the [Online Compiler page](developing-mbed-online-compiler.html).