Set LIB_INSTALL_DIR for cmake-based projects (JuliaLang#18047)

* Set LIB_INSTALL_DIR for cmake-based projects

This fixes `MULTIARCH_INSTALL=1` installations that place libraries not
into `<prefix>/lib` but into `<prefix>/lib/<host-triplet>`, like Debian
and Ubuntu.  Without this change, `libgit2`, `libssh2` and `mbedtls`
would place libraries into `<prefix>/lib`, silently failing until the
Julia bootstrap process attempted to dlopen one of them.

* Apply `LIB_INSTALL_DIR` to `CMAKE_COMMON`

deps/Makefile

@@ -46,7 +46,7 @@ CONFIGURE_COMMON += F77="$(FC)" CC="$(CC) $(DEPS_CFLAGS)" CXX="$(CXX) $(DEPS_CXX
 CMAKE_CC_ARG := $(CC_ARG) $(DEPS_CFLAGS)
 CMAKE_CXX_ARG := $(CXX_ARG) $(DEPS_CXXFLAGS)
 
-CMAKE_COMMON := -DCMAKE_INSTALL_PREFIX:PATH=$(build_prefix) -DCMAKE_PREFIX_PATH=$(build_prefix)
+CMAKE_COMMON := -DCMAKE_INSTALL_PREFIX:PATH=$(build_prefix) -DCMAKE_PREFIX_PATH=$(build_prefix) -DLIB_INSTALL_DIR=$(build_shlibdir)
 ifneq ($(VERBOSE), 0)
 CMAKE_COMMON += -DCMAKE_VERBOSE_MAKEFILE=ON
 endif

deps/libssh2.mk

@@ -8,7 +8,7 @@ LIBSSH2_OBJ_SOURCE := $(BUILDDIR)/$(LIBSSH2_SRC_DIR)/src/libssh2.$(SHLIB_EXT)
 LIBSSH2_OBJ_TARGET := $(build_shlibdir)/libssh2.$(SHLIB_EXT)
 
 LIBSSH2_OPTS := $(CMAKE_COMMON) -DBUILD_SHARED_LIBS=ON -DBUILD_EXAMPLES=OFF \
- -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_LIBDIR=lib
+ -DCMAKE_BUILD_TYPE=Release
 
 ifeq ($(OS),WINNT)
 LIBSSH2_OPTS += -DCRYPTO_BACKEND=WinCNG -DENABLE_ZLIB_COMPRESSION=OFF