Where does eclipse CDT stores CMake toolchain information?

CDT stores cmake toolchain information as part of org.eclipse.cdt.cmake.core.prefs file.

/Users/kondal/runtime-EclipseApplication6/.metadata/.plugins/org.eclipse.core.runtime/.settings/org.eclipse.cdt.cmake.core.prefs

For example, here is the content of the file 

cmakeToolchains/14/__path=/Users/kondal/esp/esp-idf/tools/cmake/toolchain-esp32.cmake

cmakeToolchains/14/cdt.toolChain.id=gcc-xtensa-/Users/kondal/esp/xtensa-esp32-elf/bin/xtensa-esp32-elf-gcc

cmakeToolchains/14/cdt.toolChain.type=org.eclipse.cdt.build.gcc

cmakeToolchains/n=15

eclipse.preferences.version=1

To understand more how eclipse store preferences:
https://gnu-mcu-eclipse.github.io/developer/eclipse/runtime-preferences/