[Bug] cmake does not search for libblosc or libszip

[bmcandr]

Currently, cmake does not search for Blosc or SZip libraries due to use of bang (!) rather than NOT for negation on lines 1072 and 1084 of CMakeLists.txt:

netcdf-c/CMakeLists.txt

Lines 1071 to 1081 in 5265520

	# See if we have libblosc
	IF(!MSVC)
	FIND_PACKAGE(Blosc)
	ENDIF()
	# Define a test flag for have blosc library
	IF(Blosc_FOUND)
	INCLUDE_DIRECTORIES(${Blosc_INCLUDE_DIRS})
	SET(ENABLE_BLOSC TRUE)
	ELSE()
	SET(ENABLE_BLOSC FALSE)
	ENDIF()

netcdf-c/CMakeLists.txt

Lines 1084 to 1095 in 5265520

	IF(!MSVC)
	#FIND_PACKAGE(SZIP)
	#FIND_LIBRARY(SZIP PATH NAMES szip sz)
	SET(SZIP_LIBRARY ${SZIP})
	ENDIF()
	# Define a test flag for have szip library
	IF(SZIP_FOUND)
	INCLUDE_DIRECTORIES(${SZIP_INCLUDE_DIRS})
	SET(ENABLE_SZIP TRUE)
	ELSE()
	SET(ENABLE_SZIP FALSE)
	ENDIF()

cmake's docs indicate negation is performed with the unary operator NOT: https://cmake.org/cmake/help/latest/command/if.html

I will open a pull request shortly to fix this.

Related to #2234 and Unidata/netcdf-fortran#328

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Version: master branch (5265520)
OS: Mac OS 11.6.4 + 12.3, SUSE Linux Enterprise Server 12.3
Compiler: GCC 11.2.0