CMakeLists.txt: eliminate floating dependencies

Prior to this, the respective build options would get enabled depending
on whether or not these components were found on the build system.

I believe it's better to make them strict (add REQUIRED parameter),
so that rpm builds are always deterministic, subject to cmake options.

Resolves: rpm-software-management#2855

CMakeLists.txt

@@ -32,6 +32,13 @@ option(WITH_IMAEVM "Build with IMA support" OFF)
 option(WITH_FAPOLICYD "Build with fapolicyd support" ON)
 option(WITH_INTERNAL_OPENPGP "Use internal OpenPGP parser (DEPRECATED)" OFF)
 option(WITH_READLINE "Build with readline support" ON)
+option(WITH_BZIP2 "Build with bzip2 support" ON)
+option(WITH_ICONV "Build with iconv support" ON)
+option(WITH_ZSTD "Build with zstd support" ON)
+option(WITH_LIBDW "Build with libdw support" ON)
+option(WITH_LIBELF "Build with libelf support" ON)
+option(WITH_LIBLZMA "Build with liblzma support" ON)
+option(WITH_DOXYGEN "Build with doxygen support" ON)
 
 set(RPM_CONFIGDIR "${CMAKE_INSTALL_PREFIX}/lib/rpm" CACHE PATH "rpm home")
 set(RPM_MACROSDIR "${RPM_CONFIGDIR}/macros.d")
@@ -193,19 +200,31 @@ set(REQFUNCS
 find_package(PkgConfig REQUIRED)
 find_package(Lua 5.2 REQUIRED)
 find_package(ZLIB REQUIRED)
-find_package(BZip2)
-find_package(Iconv)
+if (WITH_BZIP2)
+    find_package(BZip2 REQUIRED)
+endif()
+if (WITH_ICONV)
+    find_package(Iconv REQUIRED)
+endif()
 
 pkg_check_modules(POPT REQUIRED IMPORTED_TARGET popt)
 
 if (WITH_READLINE)
     pkg_check_modules(READLINE REQUIRED IMPORTED_TARGET readline)
 endif()
 
-pkg_check_modules(ZSTD IMPORTED_TARGET libzstd>=1.3.8)
-pkg_check_modules(LIBELF IMPORTED_TARGET libelf)
-pkg_check_modules(LIBDW IMPORTED_TARGET libdw)
-pkg_check_modules(LIBLZMA IMPORTED_TARGET liblzma>=5.2.0)
+if (WITH_ZSTD)
+    pkg_check_modules(ZSTD REQUIRED IMPORTED_TARGET libzstd>=1.3.8)
+endif()
+if (WITH_LIBELF)
+    pkg_check_modules(LIBELF REQUIRED IMPORTED_TARGET libelf)
+endif()
+if (WITH_LIBDW)
+    pkg_check_modules(LIBDW REQUIRED IMPORTED_TARGET libdw)
+endif()
+if (WITH_LIBLZMA)
+    pkg_check_modules(LIBLZMA REQUIRED IMPORTED_TARGET liblzma>=5.2.0)
+endif()
 pkg_check_modules(LIBARCHIVE REQUIRED IMPORTED_TARGET libarchive)
 
 # Lua module does not ship an IMPORTED target, define our own

docs/CMakeLists.txt

@@ -3,7 +3,9 @@ mark_as_advanced(PANDOC)
 
 add_subdirectory(man)
 
-find_package(Doxygen)
+if (WITH_DOXYGEN)
+    find_package(Doxygen REQUIRED)
+endif()
 if (DOXYGEN_FOUND)
 	# XXX API docs should be pre-built in tarballs
 	file(GLOB headers ${CMAKE_SOURCE_DIR}/include/rpm/*.h)