pcre.cmake: always check the library with check_library_exists()

even if pkg-config has it. otherwise build dependencies
aren't detected.

cmake/pcre.cmake

@@ -81,18 +81,15 @@ MACRO (CHECK_PCRE)
       FIND_PACKAGE(PkgConfig QUIET)
       PKG_CHECK_MODULES(PCRE libpcre2-8)
       # in case pkg-config or libpcre2-8.pc is not installed:
-      IF(NOT PCRE_FOUND)
-        UNSET(PCRE_FOUND CACHE)
-        CHECK_LIBRARY_EXISTS(pcre2-8 pcre2_match_8 "" PCRE_FOUND)
-      ENDIF()
+      CHECK_LIBRARY_EXISTS(pcre2-8 pcre2_match_8 "${PCRE_LIBRARY_DIRS}" HAVE_PCRE2_MATCH_8)
     ENDIF()
-    IF(NOT PCRE_FOUND OR WITH_PCRE STREQUAL "bundled")
+    IF(NOT HAVE_PCRE2_MATCH_8 OR WITH_PCRE STREQUAL "bundled")
       IF (WITH_PCRE STREQUAL "system")
         MESSAGE(FATAL_ERROR "system pcre2-8 library is not found or unusable")
       ENDIF()
       BUNDLE_PCRE2()
     ELSE()
-      CHECK_LIBRARY_EXISTS(pcre2-posix PCRE2regcomp "" NEEDS_PCRE2_DEBIAN_HACK)
+      CHECK_LIBRARY_EXISTS(pcre2-posix PCRE2regcomp "${PCRE_LIBRARY_DIRS}" NEEDS_PCRE2_DEBIAN_HACK)
       IF(NEEDS_PCRE2_DEBIAN_HACK)
         SET(PCRE2_DEBIAN_HACK "-Dregcomp=PCRE2regcomp -Dregexec=PCRE2regexec -Dregerror=PCRE2regerror -Dregfree=PCRE2regfree")
       ENDIF()