RPM change package name, without changing extracted directory

I've started creating RPMs of software that I use, to allow me to be able to deploy it configured exactly how I want. However I can't figure out how to rename the package without also renaming the tarball that RPM builds it from.

For example I have the source of PHP5.6 in a tarball php-5.6.0RC3.tar.gz. During the RPM build process this gets extracted to the directory php-5.6.0RC3 and the build process cd's into that directory to make it.

I want to change the package name to phpcustom, and still have it built from php-5.6.0RC3.tar.gz. The extract process works, but then the build process tries to cd into the directory phpcustom-5.6.0RC3 which obviously doesn't exist, and so it breaks.

How do I tell the rpmbuild which directory the build should take place in?

I guess I could just move the php-5.6.0RC3 directory to be phpcustom-5.6.0RC3 …but it seems a bit silly.

I've put my spec file below, just in case it is relevant.

%define        __spec_install_post %{nil}
%define          debug_package %{nil}
%define        __os_install_post %{_dbpath}/brp-compress

Summary: Custom built PHP with APCU
Name: php
#Name: phpcustom - this doesn't work
Provides: php
Conflicts: php
Version: 5.6.0RC3
Release: 1
License: None
Group: Development/Tools

Requires: bzip2, libcurl, libxml2

SOURCE0 : http://downloads.php.net/tyrael/php-5.6.0RC3.tar.gz
SOURCE1:        php.ini
SOURCE2:        php-cli.ini
SOURCE3:        apcu-4.0.6.tgz
URL: http://php.net/


%description
%{summary}

%prep
%setup -q -n php-%{version}
%setup -T -D -a 3

%build
mkdir -p  %{buildroot}
./configure  \
                --disable-cgi \
                --disable-debug \
                --disable-rpath \
                --disable-xmlreader \
                --disable-xmlwriter \
                --disable-xml \
                --enable-fpm \
                --enable-intl \
                --enable-json \
                --enable-mbregex \
                --enable-mbstring \
                --enable-pcntl \
                --enable-pdo \
                --enable-sockets \
                --enable-sysvsem \
                --enable-sysvshm \
                --enable-zip \
                --with-apcu \
                --with-bz2 \
                --with-config-file-path=/etc \
                --with-curl \
                --with-freetype-dir=/usr/lib \
                --with-gd \
                --with-jpeg-dir=/usr/lib \
                --with-mcrypt \
                --with-png-dir=/usr/lib \
                --with-pdo-mysql \
                --with-zlib \
                --with-mhash \
                --with-mysql \
                --with-mysqli=mysqlnd \
                --with-openssl \
                --with-pcre-regex \
                --without-pear \
                --without-zlib \
                --enable-maintainer-zts
make -j4


%install
rm -rf %{buildroot}
mkdir -p %{buildroot}%{_initrddir}
install -Dp -m0755 sapi/fpm/init.d.php-fpm.in %{buildroot}%{_initrddir}/php-fpm
%{__make} install INSTALL_ROOT="%{buildroot}"
cp %{SOURCE1} %{buildroot}/etc/php.ini
cp %{SOURCE2} %{buildroot}/etc/php-cli.ini

%post
%/sbin/chkconfig --add php-fpm
%/sbin/chkconfig --level 2345 php-fpm on


%clean
 rm -rf %{buildroot}


%preun
if [ "$1" = 0 ] ; then
    /sbin/service php-fpm stop > /dev/null 2>&1
    /sbin/chkconfig --del php-fpm
fi
exit 0

%postun
if [ "$1" -ge 1 ]; then
    /sbin/service php-fpm condrestart > /dev/null 2>&1
fi
exit 0



%files
%defattr(-,root,root,-)
%config(noreplace) %{_sysconfdir}/php.ini
%config(noreplace) %{_sysconfdir}/php-cli.ini
/etc/rc.d/init.d/php-fpm
/usr/local/bin/*
/usr/local/etc/*
/usr/local/include/php/*
/usr/local/lib/php/build/*
/usr/local/php/fpm/*
/usr/local/php/man/man1/*
/usr/local/php/man/man8/*
/usr/local/sbin/*
/usr/local/lib/php/extensions/no-debug-zts-20131226/opcache.a
/usr/local/lib/php/extensions/no-debug-zts-20131226/opcache.so


%changelog
* Thu Apr 24 2009  Elia Pinto <devzero2000@rpm5.org> 1.0-1
- First Build

EOF