Improve ELF shared library handling

Improve ELF shared library handling

Pass in -rpath-link option to the linker so that blkid will build
correctly on systems that don't have libcom_err.so.2 installed.

Fix debugfs to only try to link with -ldl when building without shared
libraries; with ELF shared libraries, the library which requires -ldl
(libss.so) can required the library dependency itself.

Fix how we build tune2fs.static so that we use @LDFLAG_STATIC@, via
$(LDFLAGS_STATIC), instead of hard-coding the use of -static.

Addresses-Sourceforge-Bug: #2088537

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>