Try absolute dir for doxygen

docs/libcopp.doxyfile.in

@@ -780,7 +780,7 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = ..
+INPUT                  = @PROJECT_SOURCE_DIR@
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses
@@ -820,8 +820,8 @@ RECURSIVE              = YES
 # Note that relative paths are relative to the directory from which doxygen is
 # run.
 
-EXCLUDE                = ../docs/sphinx \
-                         ../build \
+EXCLUDE                = @PROJECT_SOURCE_DIR@/docs/sphinx \
+                         @PROJECT_SOURCE_DIR@/build \
                          sphinx
 
 
@@ -839,7 +839,7 @@ EXCLUDE_SYMLINKS       = NO
 # Note that the wildcards are matched against the file with absolute path, so to
 # exclude all test directories for example use the pattern */test/*
 
-EXCLUDE_PATTERNS       = */build*/*
+EXCLUDE_PATTERNS       = @PROJECT_SOURCE_DIR@/build*
 
 # The EXCLUDE_SYMBOLS tag can be used to specify one or more symbol names
 # (namespaces, classes, functions, etc.) that should be excluded from the
@@ -856,7 +856,7 @@ EXCLUDE_SYMBOLS        =
 # that contain example code fragments that are included (see the \include
 # command).
 
-EXAMPLE_PATH           = ../sample
+EXAMPLE_PATH           = @PROJECT_SOURCE_DIR@/sample
 
 # If the value of the EXAMPLE_PATH tag contains directories, you can use the
 # EXAMPLE_PATTERNS tag to specify one or more wildcard pattern (like *.cpp and