Update LDFLAGS in Makefile.linux to prevent compiling error for Slr

[shkao]

Hello,

I'm aware of the conda way to install external programs for ete-build.
However I'd like to make a custom Dockerfile for it.
To prevent the following error when compiling Slr in Linux when running ete3 upgrade-external-tools (after the installation of libblas-dev and liblapack-dev):

/usr/bin/ld: matrix.o: undefined reference to symbol 'dgemm_'
//usr/lib/libblas.so.3: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
Makefile.linux:16: recipe for target 'Slr' failed
make: *** [Slr] Error 1
cp: cannot stat ‘../bin/Slr’: No such file or directory
ls: cannot access /root/.etetoolkit/ext_apps-latest/bin/Slr: No such file or directory

Would it be possible to change the 8th line of Makefile.linux
from LDFLAGS = -L$(BLASDIR) -lblas -llapack -lm
to LDFLAGS = -L/usr/lib/lapack -llapack -L/usr/lib/libblas -lblas -lm ?

The above modification is a workaround suggested by dsalazar23491.

[shkao]

Or is there a way to skip the installation of Slr if it's already in $PATH when running ete3 upgrade-external-tools?