Error return value of `specTmpl.Execute` is not checked (errcheck)

Error return value of `specTmpl.Execute` is not checked (errcheck)

issues found

=== RUN TestWindows === PAUSE TestWindows === CONT TestWindows --- FAIL: TestWindows (38.55s)

=== RUN TestWindows/test_windows_signing === PAUSE TestWindows/test_windows_signing === CONT TestWindows/test_windows_signing builld.go:155: #1 [internal] load .dockerignore builld.go:155: #1 transferring context: 134B done builld.go:155: #1 DONE 0.0s builld.go:155: builld.go:155: #2 resolve image config for docker-image://docker.io/library/golang:1.22 builld.go:155: #2 DONE 0.1s builld.go:155: builld.go:155: #3 resolve image config for docker-image://docker.io/library/golang:1.21 builld.go:155: #3 DONE 0.1s builld.go:155: builld.go:155: #2 resolve image config for docker-image://docker.io/library/golang:1.22 builld.go:155: #2 DONE 0.2s builld.go:155: builld.go:155: #2 resolve image config for docker-image://docker.io/library/golang:1.22 builld.go:155: #2 DONE 0.3s builld.go:155: builld.go:155: #4 local://dockerfile builld.go:155: #4 transferring dockerfile: 32B done builld.go:155: #4 DONE 0.0s builld.go:155: builld.go:155: #5 [internal] load metadata for mcr.microsoft.com/oss/go/microsoft/golang:1.21@sha256:a7b065117cd8759f0694fb18eea3cf2b7148c5fc65920d60a13bf1b0786edda7 builld.go:155: #5 DONE 0.0s builld.go:155: builld.go:155: #6 [go 1/1] FROM mcr.microsoft.com/oss/go/microsoft/golang:1.21@sha256:a7b065117cd8759f0694fb18eea3cf2b7148c5fc65920d60a13bf1b0786edda7 builld.go:155: #6 resolve mcr.microsoft.com/oss/go/microsoft/golang:1.21@sha256:a7b065117cd8759f0694fb18eea3cf2b7148c5fc65920d60a13bf1b0786edda7 done builld.go:155: #6 DONE 0.0s builld.go:155: builld.go:155: #7 [frontend 2/2] COPY --from=frontend-build /dalec-redirectio /dalec-redirectio builld.go:155: #7 CACHED builld.go:155: builld.go:155: #8 [internal] load build context builld.go:155: #8 transferring context: 4.93kB 0.0s done builld.go:155: #8 DONE 0.0s builld.go:155: builld.go:155: #9 mkfile /Dockerfile builld.go:155: #9 DONE 0.0s builld.go:155: builld.go:155: #10 resolve image config for docker-image://mcr.microsoft.com/cbl-mariner/base/core:2.0 builld.go:155: #10 DONE 1.1s builld.go:155: builld.go:155: #11 Building mariner2 container: bar builld.go:155: #11 resolve mcr.microsoft.com/cbl-mariner/base/core:2.0 builld.go:155: #11 resolve mcr.microsoft.com/cbl-mariner/base/core:2.0 1.0s done builld.go:155: #11 DONE 1.0s builld.go:155: builld.go:155: #12 Tar gomod deps builld.go:155: #12 CACHED builld.go:155: builld.go:155: #13 Tar gomod deps builld.go:155: #13 CACHED builld.go:155: builld.go:155: #14 copy / /SOURCES builld.go:155: #14 CACHED builld.go:155: builld.go:155: #15 Building mariner2 container: bar builld.go:155: #15 CACHED builld.go:155: builld.go:155: #16 Generate RPM spec builld.go:155: #16 DONE 0.9s builld.go:155: builld.go:155: #17 Generate RPM spec builld.go:155: #17 DONE 0.2s builld.go:155: builld.go:155: #18 Build RPM builld.go:155: #18 0.170 Checking for unpackaged file(s): /usr/lib/rpm/check-files /build/tmp/work builld.go:155: builld.go:155: #18 0.181 Wrote: /build/out/SRPMS/bar-0.0.1-1.cm2.src.rpm builld.go:155: builld.go:155: #18 0.251 Executing(%clean): /bin/sh -e /var/tmp/rpm-tmp.cmAsUZ builld.go:155: builld.go:155: #18 0.254 + umask 022 builld.go:155: builld.go:155: #18 0.254 + cd /build/top/BUILD builld.go:155: