[Howto] read the search-path for building-tools (cpp, gcc, ld)

c-preprocessor (GNU cpp)

environment-variable: $CPATH

#cpp -v
/usr/include

compiler (GNU cc)

environment-variable: $CPATH

#gcc -E -Wp,-v -
/usr/include

linker (GNU ld)

environment-variable: $LIBRARY_PATH

#ld --verbose | grep -i 'search_dir'
SEARCH_DIR("/lib"); SEARCH_DIR("/usr/lib"); SEARCH_DIR("/usr/local/lib")