1027 - Cannot use <%s> to modify <%s> for Variable '%s'.

Description
An attempt was made to modify a variable with a differing type, where such an operation is not supported.
Example
Config:
.MyVar = 'string' .MyVar + 7
Output:
c:\Test\fbuild.bff(2):(8) FASTBuild Error #1027 - Cannot use <Int> to modify <Any> for Variable '.MyVar'. .MyVar + 7 ^ \--here
Fix:
.MyVar = 'string' .MyVar + 'another string'