使用了 mathspec 宏包更改了数学字体，但是向量加粗的效果无法实现。比如公式中对 v 使用了加粗命令\boldsymbol{v}，但是并没有效果。如果使用\textbf{\textit{v}}命令，则可以加粗，但是我不想这样做。有什么好的方法实现这个向量加粗的效果？或者说为什么\boldsymbol命令无效了呢？

\documentclass{article}

\usepackage{amsmath}
\usepackage[MnSymbol]{mathspec}%选项是调用了 MnSymbol 包
\setallmainfonts{Minion Pro}%需要 Minion Pro 字体

% from fourier.sty, adapted
\DeclareFontEncoding{FMX}{}{}
\DeclareFontSubstitution{FMX}{futm}{m}{n}
\DeclareSymbolFont{fourierlargesymbols}{FMX}{futm}{m}{n}
% from fontdef.dtx, adapted
\DeclareMathSymbol{\intop}{\mathop}{fourierlargesymbols}{"52}

\begin{document}
I can eat glass, it doesn't hurt me. I can eat glass, it doesn't hurt me. I can eat glass, it doesn't hurt me. I can eat glass, it doesn't hurt me. I can eat glass, it doesn't hurt me.
\[
    \rho_\infty \boldsymbol{v}_\infty \delta^* = \int_0^\infty\left(\rho_\infty v_\infty - \rho u\right)\mathrm{d}y.
\]
I can eat glass, it doesn't hurt me. I can eat glass, it doesn't hurt me. I can eat glass, it doesn't hurt me. I can eat glass, it doesn't hurt me. I can eat glass, it doesn't hurt me. 
\end{document}