Make sure BBHx knows how to link locally-installed LAPACK (#4855)

* Make sure BBHx knows how to link locally-installed LAPACK

* Woops, fix a mistake

* That did not work, but this looks better

tox.ini

@@ -38,6 +38,10 @@ conda_deps=
     gsl
     lapack==3.6.1
 conda_channels=conda-forge
+setenv =
+    ; Tell the linker to look for shared libs inside the temporary Conda env.
+    ; Needed to build BBHx's wheel, whick links to LAPACK.
+    LIBRARY_PATH={envdir}/lib:{env:LIBRARY_PATH:}
 commands = pytest
 
 # The following are long running or may require
@@ -81,5 +85,9 @@ conda_deps=
     lapack==3.6.1
     openmpi
 conda_channels=conda-forge
-setenv = PYCBC_TEST_TYPE=docs
+setenv =
+    PYCBC_TEST_TYPE=docs
+    ; Tell the linker to look for shared libs inside the temporary Conda env.
+    ; Needed to build BBHx's wheel, whick links to LAPACK.
+    LIBRARY_PATH={envdir}/lib:{env:LIBRARY_PATH:}
 commands = bash tools/pycbc_test_suite.sh