Install the prerequisite packages to compile the module. Installing apache2-dev should do the job:

apt-get install apache2-dev

I had some problems with a missing libtool script so I had to link it:

cd /usr/share/apache2/build
ln -s /usr/lib/libtool .

Download the fastcgi extension from http://www.fastcgi.com/ and unpack the tar.gz:

wget http://www.fastcgi.com/dist/mod_fastcgi-X.X.X.tar.gz
tar -xzf mod_fastcgi-X.X.X.tar.gz
cd mod_fastcgi-X.X.X

Note: Due a bug in fastcgi you need at least snapshot from mid April 2004 or the upcoming 2.4.3 release.

Copy Makefile.AP2 to Makefile:

cp Makefile.AP2 Makefile

Modify Makefile for Apache 2 to reflect the system configuration:

#
#  Makefile for Apache2
#

builddir     = .

# XXX change this line
top_dir      = /usr/share/apache2


top_srcdir   = ${top_dir}
top_builddir = ${top_dir}

include ${top_builddir}/build/special.mk

APXS      = apxs
APACHECTL = apachectl

#DEFS=-Dmy_define=my_value
#INCLUDES=-Imy/include/dir
#LIBS=-Lmy/lib/dir -lmylib

# XXX add this line
INCLUDES=-I /usr/include/apache2 -I /usr/include/apr-0

all: local-shared-build

install: install-modules

clean:
        -rm -f *.o *.lo *.slo *.la

Run make and install the modules:

make
make install

Now you should have a module called mod_fastcgi.so in /usr/lib/apache2/modules.