set OPENBLAS_CMAKE_DIR to <prefix>/lib/cmake/<package_name>

usually these files are more often located in this subdir

Makefile.install

@@ -9,7 +9,7 @@ OPENBLAS_INCLUDE_DIR := $(PREFIX)/include
 OPENBLAS_LIBRARY_DIR := $(PREFIX)/lib
 OPENBLAS_BINARY_DIR := $(PREFIX)/bin
 OPENBLAS_BUILD_DIR := $(CURDIR)
-OPENBLAS_CMAKE_DIR := $(PREFIX)/cmake
+OPENBLAS_CMAKE_DIR := $(OPENBLAS_LIBRARY_DIR)/cmake/openblas
 OPENBLAS_CMAKE_CONFIG := OpenBLASConfig.cmake
 
 .PHONY : install