Fix issue with chplconfig not supporting variables with equals signs (#…

…26178)

Fixes an issue where if a `chplconfig` file has a variable with a value
that contains an equals sign, it will break with an error like `Warning:
Syntax Error: $CHPL_HOME/chplconfig:line`.

This resolves an issue a user saw on a system where
`--gcc-toolchain=...` was apart of the definition for
`CHPL_TARGET_CC/CXX`

[Reviewed by @e-kayrakli]

util/chplenv/overrides.py

@@ -184,7 +184,7 @@ def parse(self):
                 if self.skip_line(line, linenum):
                     continue
 
-                var, val = [f.strip() for f in line.split('=')]
+                var, val = [f.strip() for f in line.split('=', maxsplit=1)]
                 self.chplconfig[var] = val
 
     def skip_line(self, line, linenum):
@@ -198,7 +198,7 @@ def skip_line(self, line, linenum):
 
         # Check for syntax errors
         try:
-            var, val = [f.strip() for f in line.split('=')]
+            var, val = [f.strip() for f in line.split('=', maxsplit=1)]
         except ValueError:
             self.warnings.append(
             (