Make specifying the CMake components optional.

cmake/pcre2-config.cmake.in

@@ -7,9 +7,13 @@
 # -----------------
 # To make use of the static library instead of the shared one, one needs
 # to set the variable PCRE2_USE_STATIC_LIBS to ON before calling find_package.
+#
+# The following components are supported: 8BIT, 16BIT, 32BIT and POSIX.
+# They used to be required but not anymore; all available targets will
+# be defined regardless of the requested components.
 # Example:
 #   set(PCRE2_USE_STATIC_LIBS ON)
-#   find_package(PCRE2 CONFIG COMPONENTS 8BIT)
+#   find_package(PCRE2 CONFIG)
 #
 # This will define the following variables:
 #
@@ -51,13 +55,6 @@ _pcre2_add_component_target(16BIT 16)
 _pcre2_add_component_target(32BIT 32)
 _pcre2_add_component_target(POSIX posix)
 
-# Check if at least one component has been specified.
-list(LENGTH PCRE2_FIND_COMPONENTS PCRE2_NCOMPONENTS)
-if (PCRE2_NCOMPONENTS LESS 1)
-  message(FATAL_ERROR "No components have been specified. This is not allowed. Please, specify at least one component.")
-endif ()
-unset(PCRE2_NCOMPONENTS)
-
 # When POSIX component has been specified make sure that also 8BIT component is specified.
 set(PCRE2_8BIT_COMPONENT FALSE)
 set(PCRE2_POSIX_COMPONENT FALSE)