[1.7.1] Fix LAPACK functionality detection from static OpenBLAS (pytorch#48819)

Summary:
BLAS `sgemm_` only depends on pthreads, but LAPACK `cheev_` also depends on libm

Pull Request resolved: pytorch#46710

Reviewed By: walterddr

Differential Revision: D24476082

Pulled By: malfet

fbshipit-source-id: e0b91116f18bbcdabb1f99c2ec9d98283df4393f

Author: malfet

cmake/Dependencies.cmake

@@ -1623,6 +1623,7 @@ if(NOT INTERN_BUILD_MOBILE)
   find_package(LAPACK)
   if(LAPACK_FOUND)
     set(USE_LAPACK 1)
+    list(APPEND Caffe2_PRIVATE_DEPENDENCY_LIBS ${LAPACK_LIBRARIES})
   endif()
 
   if(NOT USE_CUDA)

cmake/Modules/FindBLAS.cmake

@@ -153,7 +153,7 @@ if((NOT BLAS_LIBRARIES)
   BLAS
   sgemm
   ""
-  "openblas;pthread")
+  "openblas;pthread;m")
   if(BLAS_LIBRARIES)
     set(BLAS_INFO "open")
   endif(BLAS_LIBRARIES)

cmake/Modules/FindLAPACK.cmake

@@ -123,6 +123,30 @@ if(BLAS_FOUND)
   IF((NOT LAPACK_INFO) AND (BLAS_INFO STREQUAL "open"))
     SET(CMAKE_REQUIRED_LIBRARIES ${BLAS_LIBRARIES})
     check_function_exists("cheev_" OPEN_LAPACK_WORKS)
+    if(OPEN_LAPACK_WORKS)
+      check_function_exists("cgesdd_" LAPACK_CGESDD_WORKS)
+      if(NOT LAPACK_CGESDD_WORKS)
+        find_library(GFORTRAN_LIBRARY
+          NAMES libgfortran.a gfortran
+          PATHS /usr/lib/gcc/aarch64-linux-gnu/9/
+                /usr/lib/gcc/x86_64-redhat-linux/9/
+                /usr/lib/gcc/aarch64-linux-gnu/8/
+                /usr/lib/gcc/x86_64-redhat-linux/8/
+                /usr/lib/gcc/aarch64-linux-gnu/7/
+                /usr/lib/gcc/x86_64-redhat-linux/7/
+                )
+       list(APPEND CMAKE_REQUIRED_LIBRARIES "${GFORTRAN_LIBRARY}")
+       unset(LAPACK_CGESDD_WORKS CACHE)
+       check_function_exists("cgesdd_" LAPACK_CGESDD_WORKS)
+       if(LAPACK_CGESDD_WORKS)
+         list(APPEND LAPACK_LIBRARIES "${GFORTRAN_LIBRARY}")
+       else()
+         message(WARNING "OpenBlas has been compiled with Lapack support, but cgesdd can not be used")
+         set(OPEN_LAPACK_WORKS NO)
+       endif()
+      endif()
+    endif()
+
     set(CMAKE_REQUIRED_LIBRARIES)
     if(OPEN_LAPACK_WORKS)
       SET(LAPACK_INFO "open")