[CYGWIN] [BUILD] deps/blastrampoline: Fix build with USE_BINARYBUILDER_BLASTRAMPOLINE=0 (#49938)
Error:
```
cp: cannot stat 'libblastrampoline.dll': No such file or directory
```
Build commands:
```
cd ~/devel/julia && \
git clean -ffxd --exclude=srccache --exclude=scratch && \
[[ -d "./usr-staging" ]] && rm -rf "./usr-staging" ; \
[[ -d "./usr" ]] && rm -rf "./usr" ; \
[[ -d "./deps/srccache/blastrampoline.git" ]] && rm -rf "./deps/srccache/blastrampoline.git" ; \
[[ -d "./deps/scratch/blastrampoline" ]] && rm -rf "./deps/scratch/blastrampoline" ; \
[[ -d "./deps/scratch/SuiteSparse-5.10.1" ]] && rm -rf "./deps/scratch/SuiteSparse-5.10.1" ; \
git checkout master && \
git log -1 --format=oneline && \
echo 'XC_HOST = x86_64-w64-mingw32' > Make.user && \
echo 'DEPS_GIT = 1' >> Make.user && \
echo 'USE_BINARYBUILDER_BLASTRAMPOLINE = 0' >> Make.user && \
echo 'USE_BINARYBUILDER_LIBSUITESPARSE = 0' >> Make.user && \
make -C deps install-csl && \
cp /usr/x86_64-w64-mingw32/sys-root/mingw/lib/libmsvcrt.a ./usr/lib/libmsvcrt.a && \
make all --jobs=1 2>&1 | tee ../julia-master-blastrampoline-all-build.log && echo -ne '\007'
```
Tim S.