configure: quote the assignments for run-compiler

Building for multilib failed, as the compiler command contains an
extra argument. That needs quoting.

Regression from b78ca50

Fixes curl#11179
Closes curl#11180

Author: eworm-de

configure.ac

@@ -193,8 +193,8 @@ dnl something different but only have that affect the execution of the results
 dnl of the compile, not change the libraries for the compiler itself.
 dnl
 compilersh="run-compiler"
-echo "CC=$CC" > $compilersh
-echo "LD_LIBRARY_PATH=$LD_LIBRARY_PATH" >> $compilersh
+echo "CC=\"$CC\"" > $compilersh
+echo "LD_LIBRARY_PATH=\"$LD_LIBRARY_PATH\"" >> $compilersh
 echo 'exec $CC $@' >> $compilersh
 
 dnl **********************************************************************