I found that the directories specified by the configuration 
of GCC or by LIBRARY_PATH variable override these specified 
with -L command line switch.
example:

Release:
gcc-2.95.2

Environment:
/tmp>gcc -dumpspecs
*asm:
%{v:-V} %{Qy:} %{!Qn:-Qy} %{n} %{T} %{Ym,*} %{Yd,*} %{Wa,*:%*}

*asm_final:
%|

*cpp:
%(cpp_cpu) %{fPIC:-D__PIC__ -D__pic__} %{fpic:-D__PIC__ -D__pic__} %{posix:-D_POSIX_SOURCE} %{pthread:-D_REENTRANT}

*cc1:
%(cc1_cpu) %{profile:-p}

*cc1plus:


*endfile:
%{!shared:crtend.o%s} %{shared:crtendS.o%s} crtn.o%s

*link:
-m elf_i386 %{shared:-shared}   %{!shared:     %{!ibcs:       %{!static:        %{rdynamic:-export-dynamic}       %{!dynamic-linker:-dynamic-linker /lib/ld-linux.so.2}}  %{static:-static}}}

*lib:
%{shared: -lc}    %{!shared: %{mieee-fp:-lieee} %{pthread:-lpthread}    %{profile:-lc_p} %{!profile: -lc}}

*libgcc:
-lgcc

*startfile:
%{!shared:      %{pg:gcrt1.o%s} %{!pg:%{p:gcrt1.o%s}                   %{!p:%{profile:gcrt1.o%s}                   %{!profile:crt1.o%s}}}}    crti.o%s %{!shared:crtbegin.o%s} %{shared:crtbeginS.o%s}

*switches_need_spaces:


*signed_char:
%{funsigned-char:-D__CHAR_UNSIGNED__}

*predefines:
-D__ELF__ -Dunix -D__i386__ -Dlinux -Asystem(posix)

*cross_compile:
0

*version:
2.95.2

*multilib:
. ;

*multilib_defaults:


*multilib_extra:


*multilib_matches:


*linker:
collect2

*cpp_486:
%{!ansi:-Di486} -D__i486 -D__i486__

*cpp_586:
%{!ansi:-Di586 -Dpentium}       -D__i586 -D__i586__ -D__pentium -D__pentium__

*cpp_k6:
%{!ansi:-Di586 -Dk6}    -D__i586 -D__i586__ -D__k6 -D__k6__

*cpp_686:
%{!ansi:-Di686 -Dpentiumpro}    -D__i686 -D__i686__ -D__pentiumpro -D__pentiumpro__

*cpp_cpu_default:
%(cpp_686)

*cpp_cpu:
-Acpu(i386) -Amachine(i386) %{!ansi:-Di386} -D__i386 -D__i386__ %{mcpu=i486:%(cpp_486)} %{m486:%(cpp_486)} %{mpentium:%(cpp_586)} %{mcpu=pentium:%(cpp_586)} %{mpentiumpro:%(cpp_686)} %{mcpu=pentiumpro:%(cpp_686)} %{mcpu=k6:%(cpp_k6)} %{!mcpu*:%{!m486:%{!mpentium*:%(cpp_cpu_default)}}}

*cc1_cpu:
%{!mcpu*: %{m386:-mcpu=i386 -march=i386} %{m486:-mcpu=i486 -march=i486} %{mpentium:-mcpu=pentium} %{mpentiumpro:-mcpu=pentiumpro}}

*link_command:
%{!fsyntax-only:  %{!c:%{!M:%{!MM:%{!E:%{!S:%(linker) %l %X %{o*} %{A} %{d} %{e*} %{m} %{N} %{n}                  %{r} %{s} %{t} %{u*} %{x} %{z} %{Z}                     %{!A:%{!nostdlib:%{!nostartfiles:%S}}}                    %{static:} %{L*} %D %o                  %{!nostdlib:%{!nodefaultlibs:%G %L %G}}                   %{!A:%{!nostdlib:%{!nostartfiles:%E}}}                    %{T*}
 }}}}}}

/tmp>gcc -dumpmachine
i686-pc-linux-gnu
/tmp>gcc -dumpversion
2.95.2
/tmp>uname -a
Linux iwsl011.iil.intel.com 2.2.12-20smp #2 SMP Mon Feb 14 05:41:40 PST 2000 i686 unknown

How-To-Repeat:
copy some file from /usr/lib to ~/:

Unformatted:
 >gcc -L $tools/sys/glib-1.2.7/lib --print-file-name=libglib.a
 /usr/lib/libglib.a
 >setenv LIBRARY_PATH $tools/sys/glib-1.2.7/lib
 >gcc -L $tools/sys/glib-1.2.7/lib --print-file-name=libglib.a
 /afs/iil/nike/data/tools/sys/glib-1.2.7/lib/libglib.a
 
 You see that I gave the same directory on command line
 and /usr/lib from builtin configuration did override it,
 while LIBRARY_PATH overrides both built-in and command line
 parameters!
 
 The documentation for gcc says:
 
 GCC info 7 says:
    Note that you can also specify places to search using options such as
 `-B', `-I' and `-L' (*note Directory Options::.).  These take
 precedence over places specified using environment variables, which in
 turn take precedence over those specified by the configuration of GCC.
 
 >cp /usr/lib/libglib.a ~/
 >gcc -L ~/ --print-file-name=libglib.a
 which is incorrect, because the file must be looked up
 in -L first!