PR pending https://github.com/groonga/groonga/pull/2799.patch
fix https://bugs.gentoo.org/973576
Blosc2's CMake file only accepts a requested version when the major
version matches the installed one. Requesting 2.10.0 fails even if 3.X
system version is installed and compiled fine. Rework the detection
logic.
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1446,16 +1446,15 @@ if(NOT "${GRN_WITH_BLOSC}" STREQUAL "no")
   if("${GRN_WITH_BLOSC}" STREQUAL "bundled")
     set(Blosc2_FOUND FALSE)
   else()
-    if("${GRN_WITH_BLOSC}" STREQUAL "system")
-      find_package(Blosc2 ${GRN_BLOSC_REQUIRED_VERSION} REQUIRED)
-    else()
-      find_package(Blosc2 ${GRN_BLOSC_REQUIRED_VERSION})
-    endif()
+    find_package(Blosc2 QUIET)
   endif()
-  if(Blosc2_FOUND)
+  if(Blosc2_FOUND AND Blosc2_VERSION VERSION_GREATER_EQUAL GRN_BLOSC_REQUIRED_VERSION)
     set(GRN_WITH_BLOSC TRUE)
     target_link_libraries(grn_dependencies INTERFACE Blosc2::blosc2_shared)
     message(STATUS "Blosc: system")
+  elseif("${GRN_WITH_BLOSC}" STREQUAL "system")
+    message(FATAL_ERROR
+      "Blosc2 >=${GRN_BLOSC_REQUIRED_VERSION} not found!")
   elseif(NOT FETCHCONTENT_FULLY_DISCONNECTED)
     # FETCHCONTENT_FULLY_DISCONNECTED isn't for disabling network
     # access but deb uses it...