cmake: Support UTF-8 characters in Kconfig values

We are using the CMake command 'file(STRINGS' (which defaults to only
decoding ASCII) to read Kconfig configurations. When UTF-8 characters
are detected they are treated as newlines.

This behaviour has caused issues when users have input UTF-8
characters into Kconfig values. E.g. USB device descriptor strings.

This commit adds the flag 'ENCODING "UTF-8"' to the 'file(STRINGS'
command so that UTF-8 characters are correctly passed through the
build system.

Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>

cmake/extensions.cmake

@@ -638,6 +638,7 @@ function(import_kconfig config_file)
     ${config_file}
     DOT_CONFIG_LIST
     REGEX "^CONFIG_"
+    ENCODING "UTF-8"
   )
 
   foreach (CONFIG ${DOT_CONFIG_LIST})

misc/generated/CMakeLists.txt

@@ -4,6 +4,7 @@ file(STRINGS
   ${AUTOCONF_H}
   CONFIG_LIST
   REGEX "^#define CONFIG_"
+  ENCODING "UTF-8"
   )
 foreach (CONFIG ${CONFIG_LIST})
   string(REGEX REPLACE "#define (CONFIG_[A-Z|_|0-9]*) (.*)" "GEN_ABSOLUTE_SYM(\\1, \\2)" CONFIG ${CONFIG})