Python was not found; run without arguments to install from the Microsoft Store, or disable this shortcut from Settings > Manage App Execution Aliases.
NMAKE : fatal error U1077: 'C:\Users\Lenovo\AppData\Local\Microsoft\WindowsApps\python.exe' : return code '0x2331'

C:\Qt\5.15.14\Src\build>path
PATH=C:\Python27;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.29.30133\bin\HostX64\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\VC\VCPackages;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\CommonExtensions\Microsoft\TestWindow;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Current\bin\Roslyn;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Team Tools\Performance Tools\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Team Tools\Performance Tools;C:\Program Files (x86)\Microsoft Visual Studio\Shared\Common\VSPerfCollectionTools\vs2019\\x64;C:\Program Files (x86)\Microsoft Visual Studio\Shared\Common\VSPerfCollectionTools\vs2019\;C:\Program Files (x86)\HTML Help Workshop;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\Tools\devinit;C:\Program Files (x86)\Windows Kits\10\bin\10.0.19041.0\x64;C:\Program Files (x86)\Windows Kits\10\bin\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\\MSBuild\Current\Bin;C:\Windows\Microsoft.NET\Framework64\v4.0.30319;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\Tools\;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\Program Files\Git\cmd;C:\Utils\Arc\WinRAR;C:\Utils\Arc;C:\Utils;C:\Utils\sysinternals;C:\Program Files\dotnet\;C:\Program Files\TortoiseGit\bin;C:\Users\Lenovo\AppData\Local\Microsoft\WindowsApps;;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\CommonExtensions\Microsoft\CMake\Ninja

C:\Qt\5.15.14\Src\build>where python.exe
C:\Python27\python.exe
C:\Users\Lenovo\AppData\Local\Microsoft\WindowsApps\python.exe

How it does?

Solved as recommended to install from the Microsoft Store.

Check C:\Qt\5.15.14\Src\build\qtdeclarative\src\qml.generated\release\RegExpJitTables.h its size shouldn't be zero!