Describe the bug
When tuist generates target xcconfig using tuist migration command, it ads some syntax errors, using brackets were it doesn't works:

Correct:
GCC_PREPROCESSOR_DEFINITIONS[config=Debug]="$(inherited)" "USE_FMOD=1"

Generated:
GCC_PREPROCESSOR_DEFINITIONS[config=Debug]=["$(inherited)", "USE_FMOD=1"]

Then Xcodes issues de problem:

<built-in>:388:2: note: in file included from <built-in>:388:
# 1 "<command line>" 1
 ^
<command line>:17:9: error: macro name must be an identifier
#define [, 1
        ^
<built-in>:388:2: note: in file included from <built-in>:388:
# 1 "<command line>" 1
 ^
<command line>:17:9: error: macro name must be an identifier
#define [, 1
        ^
<unknown>:0: error: could not build Objective-C module 'SwiftShims'

To Reproduce
Steps to reproduce the behavior:

1. Run tuist migration settings-to-xcconfig -p ${PROJECT_NAME}.xcodeproj -t ${PROJECT_NAME} -x ${PROJECT_NAME}.xcconfig with some project using GCC_PREPROCESSOR_DEFINITIONS
2. Make tuist generate with project settings configuration targeting the generated xcconfig path.
3. Build and see the errors