cmake string trim

CMake does not have built-in functions for trimming strings, but you can use string manipulation functions provided by CMake to achieve this.

Here's an example of how to trim leading and trailing whitespaces from a string using CMake:

# Define a string variable
set(myString "   Hello, World!   ")

# Trim leading whitespaces
string(REGEX REPLACE "^\\s+" "" myString "${myString}")

# Trim trailing whitespaces
string(REGEX REPLACE "\\s+$" "" myString "${myString}")

# Output the trimmed string
message("Trimmed string: '${myString}'")

This example uses the `string(REGEX REPLACE ...)` command to replace the leading and trailing whitespaces with an empty string. The regular expressions `"^\\s+"` and `"\\s+$"` respectively match the leading and trailing whitespaces. The `"${myString}"` argument specifies the string to operate on.

Note that this example uses regular expressions to perform the trimming, which may not be the most efficient solution for very large strings. If performance is a concern, you may want to consider using other string manipulation functions provided by CMake, such as `string(SUBSTRING ...)`.