Description of problem:
Trying to build the source rpm (librsvg2-2.42.7-4.el8.src.rpm) fails in %prep stage due to a missing dependency with git:
[root@ibm-z-118 ~]# rpmbuild -bb rpmbuild/SPECS/librsvg2.spec
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.Vxa6WO
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd /root/rpmbuild/BUILD
+ rm -rf librsvg-2.42.7
+ /usr/bin/xz -dc /root/rpmbuild/SOURCES/librsvg-2.42.7.tar.xz
+ /usr/bin/tar -xof -
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ cd librsvg-2.42.7
+ /usr/bin/chmod -Rf a+rX,u+w,g-w,o-w .
+ /usr/bin/git init -q
/var/tmp/rpm-tmp.Vxa6WO: line 45: /usr/bin/git: No such file or directory
error: Bad exit status from /var/tmp/rpm-tmp.Vxa6WO (%prep)

Version-Release number of selected component (if applicable):
librsvg2-2.42.7-4.el8.src.rpm

How reproducible:
100%

Steps to Reproduce:
1. Get the source rpm librsvg2-2.42.7-4.el8.src.rpm
2. rpm -ivh librsvg2-2.42.7-4.el8.src.rpm
3. yum-builddep librsvg2-2.42.7-4.el8.src.rpm
4. rpmbuild -bb ~/rpmbuild/SPECS/librsvg2.spec

Actual results:
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.Vxa6WO
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd /root/rpmbuild/BUILD
+ rm -rf librsvg-2.42.7
+ /usr/bin/xz -dc /root/rpmbuild/SOURCES/librsvg-2.42.7.tar.xz
+ /usr/bin/tar -xof -
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ cd librsvg-2.42.7
+ /usr/bin/chmod -Rf a+rX,u+w,g-w,o-w .
+ /usr/bin/git init -q
/var/tmp/rpm-tmp.Vxa6WO: line 45: /usr/bin/git: No such file or directory
error: Bad exit status from /var/tmp/rpm-tmp.Vxa6WO (%prep)

Expected results:
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.FUnimu
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd /root/rpmbuild/BUILD
+ rm -rf librsvg-2.42.7
+ /usr/bin/xz -dc /root/rpmbuild/SOURCES/librsvg-2.42.7.tar.xz
+ /usr/bin/tar -xof -
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ cd librsvg-2.42.7 + /usr/bin/chmod -Rf a+rX,u+w,g-w,o-w . + /usr/bin/git init -q
+ /usr/bin/git config user.name rpm-build
+ /usr/bin/git config user.email '<rpm-build>'
+ /usr/bin/git add .
+ /usr/bin/git commit -q --allow-empty -a --author 'rpm-build <rpm-build>' -m 'librsvg2-2.42.7 base'
+ /usr/bin/cat /root/rpmbuild/SOURCES/CVE-2019-20446.patch
+ /usr/bin/git apply --index -p1 -
+ /usr/bin/git commit -q -m CVE-2019-20446.patch --author 'rpm-build <rpm-build>'
+ /usr/bin/cat /root/rpmbuild/SOURCES/fix-cssparser-build.patch
+ /usr/bin/git apply --index -p1 -
+ /usr/bin/git commit -q -m fix-cssparser-build.patch --author 'rpm-build <rpm-build>'
+ sed -i -e '/profile.release/a debug = true' Cargo.toml
+ exit 0
(Continues to the next stage).

Additional info:
Tested only on RHEL 8.5 on s390x. I assume it will reproduce in all supported archs as well.

I noticed that the version tested introduced a difference in the %prep stage in the .spec file.
librsvg2-2.42.7-4.el8.src.rpm:
%prep
%autosetup n librsvg%

-p1