[Eclipse] -U in build_flags does not undefine symbols in generated project

[dogtopus]

What kind of issue is this?

• PlatformIO Core.
  If you’ve found a bug, please provide an information below.

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Configuration

Operating system: Arch Linux

PlatformIO Version (platformio --version): 4.0.0a13

Description of problem

Undefining a previously defined symbol using -U does not undefine it in the generated Eclipse project file.

Steps to Reproduce

1. Append -DA_SYMBOL -UA_SYMBOL to build_flags
2. Run pio init --ide eclipse
3. Open the generated .cproject file and check for Symbols option

Actual Results

A_SYMBOL still shows up.

Expected Results

A_SYMBOL should not appear in the list since it is already undefined

If problems with PlatformIO Build System:

The content of platformio.ini:

[env:uno]
platform = atmelavr
board = uno
framework = arduino
build_flags = -DA_SYMBOL -UA_SYMBOL

[ivankravets]

Please re-test with the latest PIO Core

pio upgrade --dev

Thanks!